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English
The basic syntax of the strncmp function is as follows:
<span><span><span class="hljs-title function_ invoke__">strncmp</span></span><span>(</span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$str1</span></span><span>, </span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$str2</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$length</span></span><span>): </span><span><span class="hljs-keyword">int</span></span><span>
</span></span>$str1: The first string.
$str2: The second string.
$length: The number of characters to compare.
The strncmp function compares two strings from the beginning, up to length characters. It can return the following values:
0: The first length characters are equal.
Greater than 0: The first length characters of $str1 are greater than those of $str2.
Less than 0: The first length characters of $str1 are less than those of $str2.
The strncmp function is case-sensitive. This means that if you compare "hello" with "Hello", even though they are identical except for the first letter, the function will still consider them different. For example:
<span><span><span class="hljs-variable">$str1</span></span><span> = </span><span><span class="hljs-string">"hello"</span></span><span>;
</span><span><span class="hljs-variable">$str2</span></span><span> = </span><span><span class="hljs-string">"Hello"</span></span><span>;
<p></span>if (strncmp($str1, </span>$str2, 5) === 0) {<br>
echo "The two strings are identical";<br>
} else {<br>
echo "The two strings are different";<br>
}<br>
</span>The output will be:
<span><span>The two strings are different
</span></span>Even though "hello" and "Hello" only differ in case, strncmp considers them unequal because it is case-sensitive by default.
If you want strncmp to be case-insensitive, you can use the strncasecmp function. strncasecmp is the case-insensitive version of strncmp and works in a similar way:
<span><span><span class="hljs-title function_ invoke__">strncasecmp</span></span><span>(</span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$str1</span></span><span>, </span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$str2</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$length</span></span><span>): </span><span><span class="hljs-keyword">int</span></span><span>
</span></span>The strncasecmp function ignores case differences when comparing the first length characters of two strings. Example:
<span><span><span class="hljs-variable">$str1</span></span><span> = </span><span><span class="hljs-string">"hello"</span></span><span>;
</span><span><span class="hljs-variable">$str2</span></span><span> = </span><span><span class="hljs-string">"Hello"</span></span><span>;
<p></span>if (strncasecmp($str1, </span>$str2, 5) === 0) {<br>
echo "The two strings are identical";<br>
} else {<br>
echo "The two strings are different";<br>
}<br>
</span>The output will be:
<span><span>The two strings are identical
</span></span>As shown, the strncasecmp function ignores case differences between "hello" and "Hello", considering them the same.
The strncmp function is case-sensitive when comparing strings.
If you need a case-insensitive comparison, use the strncasecmp function.
In practical development, it is important to choose between strncmp or strncasecmp according to your specific needs to ensure the comparison results are as expected. Understanding these functions is particularly crucial when handling user input, form data, or database query results.
