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Dans PHP, la fonction USORT () est utilisée pour personnaliser le tri des tableaux. Il est très puissant et peut trier les éléments de tableau basés sur les fonctions de comparaison définies par l'utilisateur. Mais en usage réel, nous pouvons rencontrer des erreurs de tri, qui sont généralement liées à des valeurs de retour incorrectes des fonctions de comparaison ou des structures de tableau triées. Cet article analysera certaines erreurs courantes et fournira des solutions correspondantes.
Le noyau de la fonction USORT () est une fonction de comparaison définie par l'utilisateur. Cette fonction de comparaison accepte deux paramètres représentant deux éléments dans le tableau. La fonction de comparaison doit renvoyer un entier représentant l'ordre de ces deux éléments:
La valeur de retour est inférieure à 0: signifie que le premier élément doit être en avance sur le deuxième élément.
La valeur de retour est égale à 0: signifie que les deux éléments sont égaux et que leur ordre relatif reste inchangé.
Valeur de retour supérieure à 0: signifie que le premier élément doit être suivi du deuxième élément.
Si votre fonction de comparaison ne suit pas cette règle, USORT () aura une erreur de tri. Une erreur courante est que le type de valeur de retour de la fonction de comparaison est incorrect, ou que la plage de valeur de retour ne répond pas aux exigences.
<span><span><span class="hljs-variable">$array</span></span><span> = [</span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-number">1</span></span><span>, </span><span><span class="hljs-number">2</span></span><span>];
</span><span><span class="hljs-title function_ invoke__">usort</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>, function(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>) {
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$a</span></span><span> < </span><span><span class="hljs-variable">$b</span></span><span>) </span><span><span class="hljs-keyword">return</span></span><span> -</span><span><span class="hljs-number">1</span></span><span>;
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$a</span></span><span> > </span><span><span class="hljs-variable">$b</span></span><span>) </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-number">1</span></span><span>;
</span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-string">'equal'</span></span><span>; </span><span><span class="hljs-comment">// Valeur de retour incorrecte</span></span><span>
});
</span></span>Dans l'exemple ci-dessus, «Equal» est une chaîne, et Usort () prévoit de renvoyer un entier. Cela entraînera le comportement de tri que le comportement ne sera pas cohérent avec les attentes.
Assurez-vous que la fonction de comparaison renvoie toujours des valeurs entières. La bonne façon de le faire est de retourner -1 , 0 ou 1 .
<span><span><span class="hljs-variable">$array</span></span><span> = [</span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-number">1</span></span><span>, </span><span><span class="hljs-number">2</span></span><span>];
</span><span><span class="hljs-title function_ invoke__">usort</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>, function(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>) {
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$a</span></span><span> < </span><span><span class="hljs-variable">$b</span></span><span>) </span><span><span class="hljs-keyword">return</span></span><span> -</span><span><span class="hljs-number">1</span></span><span>;
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-variable">$a</span></span><span> > </span><span><span class="hljs-variable">$b</span></span><span>) </span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-number">1</span></span><span>;
</span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-number">0</span></span><span>; </span><span><span class="hljs-comment">// Valeur de retour correcte</span></span><span>
});
</span></span>La fonction USORT () convient aux éléments de tableau de différents types, mais les résultats de tri peuvent être imprévisibles si les types d'éléments du tableau sont incohérents. Par exemple, un tableau de nombres et de chaînes peut conduire à un ordre incorrect lors du tri.
<span><span><span class="hljs-variable">$array</span></span><span> = [</span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-string">'1'</span></span><span>, </span><span><span class="hljs-number">2</span></span><span>];
</span><span><span class="hljs-title function_ invoke__">usort</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>, function(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>) {
</span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$a</span></span><span> - </span><span><span class="hljs-variable">$b</span></span><span>;
});
</span></span>Bien que USORT () essaiera de convertir le type d'un élément de tableau, si le mélange des chaînes et des nombres est impliqué dans l'opération de comparaison, cela peut conduire à des résultats inattendus.
Dans les fonctions de comparaison, le type d'éléments de tableau est explicitement converti pour assurer la cohérence de la logique de comparaison.
<span><span><span class="hljs-variable">$array</span></span><span> = [</span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-string">'1'</span></span><span>, </span><span><span class="hljs-number">2</span></span><span>];
</span><span><span class="hljs-title function_ invoke__">usort</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>, function(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>) {
</span><span><span class="hljs-keyword">return</span></span><span> (</span><span><span class="hljs-keyword">int</span></span><span>)</span><span><span class="hljs-variable">$a</span></span><span> - (</span><span><span class="hljs-keyword">int</span></span><span>)</span><span><span class="hljs-variable">$b</span></span><span>; </span><span><span class="hljs-comment">// Coulé à entier</span></span><span>
});
</span></span>Lorsque vous utilisez USORT () pour trier les tableaux multidimensionnels, vous pouvez rencontrer le problème que la structure imbriquée des éléments du tableau fait que le tri ne se déroule pas correctement. Surtout lorsque vous avez besoin de trier par un élément enfant, le tri peut échouer si la fonction de comparaison n'accède pas correctement aux éléments enfants.
<span><span><span class="hljs-variable">$array</span></span><span> = [
[</span><span><span class="hljs-string">'id'</span></span><span> => </span><span><span class="hljs-number">1</span></span><span>, </span><span><span class="hljs-string">'name'</span></span><span> => </span><span><span class="hljs-string">'Tom'</span></span><span>],
[</span><span><span class="hljs-string">'id'</span></span><span> => </span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-string">'name'</span></span><span> => </span><span><span class="hljs-string">'Jerry'</span></span><span>],
[</span><span><span class="hljs-string">'id'</span></span><span> => </span><span><span class="hljs-number">2</span></span><span>, </span><span><span class="hljs-string">'name'</span></span><span> => </span><span><span class="hljs-string">'Alice'</span></span><span>]
];
</span><span><span class="hljs-title function_ invoke__">usort</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>, function(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>) {
</span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$a</span></span><span>[</span><span><span class="hljs-string">'id'</span></span><span>] - </span><span><span class="hljs-variable">$b</span></span><span>[</span><span><span class="hljs-string">'id'</span></span><span>];
});
</span></span>Dans cet exemple, le code semble bien, mais si la structure du tableau change, telle que la clé «ID» n'existe pas ou que sa valeur est vide, elle peut entraîner une erreur de tri.
Assurez-vous que la fonction de comparaison gère toutes les situations possibles, par exemple en vérifiant si la clé existe ou en fournissant des valeurs par défaut pour éviter les erreurs.
<span><span><span class="hljs-variable">$array</span></span><span> = [
[</span><span><span class="hljs-string">'id'</span></span><span> => </span><span><span class="hljs-number">1</span></span><span>, </span><span><span class="hljs-string">'name'</span></span><span> => </span><span><span class="hljs-string">'Tom'</span></span><span>],
[</span><span><span class="hljs-string">'id'</span></span><span> => </span><span><span class="hljs-number">3</span></span><span>, </span><span><span class="hljs-string">'name'</span></span><span> => </span><span><span class="hljs-string">'Jerry'</span></span><span>],
[</span><span><span class="hljs-string">'id'</span></span><span> => </span><span><span class="hljs-number">2</span></span><span>, </span><span><span class="hljs-string">'name'</span></span><span> => </span><span><span class="hljs-string">'Alice'</span></span><span>]
];
</span><span><span class="hljs-title function_ invoke__">usort</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>, function(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>) {
</span><span><span class="hljs-keyword">return</span></span><span> (</span><span><span class="hljs-keyword">isset</span></span><span>(</span><span><span class="hljs-variable">$a</span></span><span>[</span><span><span class="hljs-string">'id'</span></span><span>]) ? </span><span><span class="hljs-variable">$a</span></span><span>[</span><span><span class="hljs-string">'id'</span></span><span>] : </span><span><span class="hljs-number">0</span></span><span>) - (</span><span><span class="hljs-keyword">isset</span></span><span>(</span><span><span class="hljs-variable">$b</span></span><span>[</span><span><span class="hljs-string">'id'</span></span><span>]) ? </span><span><span class="hljs-variable">$b</span></span><span>[</span><span><span class="hljs-string">'id'</span></span><span>] : </span><span><span class="hljs-number">0</span></span><span>);
});
</span></span>Lorsque USORT () trie le tableau, le tableau est réindexé, ce qui signifie que l'indice de tableau d'origine sera rejeté. Si vous devez conserver les clés du tableau d'origine, USORT () peut ne pas vous convenir.
<span><span><span class="hljs-variable">$array</span></span><span> = [</span><span><span class="hljs-number">3</span></span><span> => </span><span><span class="hljs-string">'apple'</span></span><span>, </span><span><span class="hljs-number">1</span></span><span> => </span><span><span class="hljs-string">'banana'</span></span><span>, </span><span><span class="hljs-number">2</span></span><span> => </span><span><span class="hljs-string">'cherry'</span></span><span>];
</span><span><span class="hljs-title function_ invoke__">usort</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>, function(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>) {
</span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-title function_ invoke__">strcmp</span></span><span>(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>);
});
</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>);
</span></span>Le code ci-dessus sortira un tableau sans l'index d'origine:
<span><span><span class="hljs-title function_ invoke__">Array</span></span><span>
(
[</span><span><span class="hljs-number">0</span></span><span>] => apple
[</span><span><span class="hljs-number">1</span></span><span>] => banana
[</span><span><span class="hljs-number">2</span></span><span>] => cherry
)
</span></span>Si vous devez conserver les clés du tableau d'origine, vous pouvez utiliser uaSort () , qui est différent d' Usort () qui gardera les clés du tableau d'origine.
<span><span><span class="hljs-variable">$array</span></span><span> = [</span><span><span class="hljs-number">3</span></span><span> => </span><span><span class="hljs-string">'apple'</span></span><span>, </span><span><span class="hljs-number">1</span></span><span> => </span><span><span class="hljs-string">'banana'</span></span><span>, </span><span><span class="hljs-number">2</span></span><span> => </span><span><span class="hljs-string">'cherry'</span></span><span>];
</span><span><span class="hljs-title function_ invoke__">uasort</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>, function(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>) {
</span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-title function_ invoke__">strcmp</span></span><span>(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>);
});
</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>);
</span></span>Cela préservera l'ordre des clés d'origine:
<span><span><span class="hljs-title function_ invoke__">Array</span></span><span>
(
[</span><span><span class="hljs-number">3</span></span><span>] => apple
[</span><span><span class="hljs-number">1</span></span><span>] => banana
[</span><span><span class="hljs-number">2</span></span><span>] => cherry
)
</span></span>Lors du tri d'un tableau contenant des décimales flottantes, des erreurs de tri peuvent se produire en raison de la limitation de précision des points flottants. Surtout lorsque la précision des nombres est très élevée, la comparaison peut ne pas être comme prévu.
<span><span><span class="hljs-variable">$array</span></span><span> = [</span><span><span class="hljs-number">1.0000001</span></span><span>, </span><span><span class="hljs-number">1.0000002</span></span><span>, </span><span><span class="hljs-number">1.0000003</span></span><span>];
</span><span><span class="hljs-title function_ invoke__">usort</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>, function(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>) {
</span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-variable">$a</span></span><span> - </span><span><span class="hljs-variable">$b</span></span><span>;
});
</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>);
</span></span>La comparaison des nombres flottants peut être affectée par la précision, ce qui entraîne des résultats de tri instables.
Utilisez la fonction rond () pour limiter le nombre de chiffres de décimales flottantes pour éviter les erreurs de tri causées par des problèmes de précision flottants.
<span><span><span class="hljs-variable">$array</span></span><span> = [</span><span><span class="hljs-number">1.0000001</span></span><span>, </span><span><span class="hljs-number">1.0000002</span></span><span>, </span><span><span class="hljs-number">1.0000003</span></span><span>];
</span><span><span class="hljs-title function_ invoke__">usort</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>, function(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-variable">$b</span></span><span>) {
</span><span><span class="hljs-keyword">return</span></span><span> </span><span><span class="hljs-title function_ invoke__">round</span></span><span>(</span><span><span class="hljs-variable">$a</span></span><span>, </span><span><span class="hljs-number">7</span></span><span>) - </span><span><span class="hljs-title function_ invoke__">round</span></span><span>(</span><span><span class="hljs-variable">$b</span></span><span>, </span><span><span class="hljs-number">7</span></span><span>); </span><span><span class="hljs-comment">// Limiter la précision</span></span><span>
});
</span><span><span class="hljs-title function_ invoke__">print_r</span></span><span>(</span><span><span class="hljs-variable">$array</span></span><span>);
</span></span>
