stristr Function: How to Use Its Second Parameter? Detailed Explanation of String vs. Array

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<p></span><?php<br>
/**</p>
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<p>How to use the second parameter of the stristr function?</p>
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<p>Detailed explanation of string vs. array usage</p>
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<p>In PHP, the stristr function searches for a substring within a string and returns the portion of the string starting from the first occurrence of that substring.</p>
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<p>Its basic usage is:</p>
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<p>string stristr(string $haystack, string $needle, bool $before_needle = false)</p>
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<p>Where:</p>
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<p>$haystack is the string to search in</p>
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<p>$needle is the string to search for</p>
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<p>$before_needle optional, if true, returns the portion before the needle</p>
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<p>Some developers wonder: Can the second parameter of stristr be an array? What’s the difference between passing a string and an array?</p>
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<p>Type restriction for stristr's second parameter</p>
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<p>The second parameter of stristr must be a string and cannot be an array. Passing an array will trigger a PHP error:</p>
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<p>Warning: stristr() expects parameter 2 to be string, array given</p>
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<p>Therefore, strictly speaking, stristr only accepts a string as its second parameter.</p>
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<p>Why the confusion about arrays?</p>
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<p>In some cases, developers want to check if a string contains any of multiple keywords. stristr only handles one string at a time.</p>
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<p>A common solution is to store multiple keywords in an array and loop through them, calling stristr for each keyword.</p>
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<p>How to implement multi-keyword matching (simulating array input)</p>
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<p>Example code:<br>
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<p>$keywords = ['apple', 'banana', 'orange'];<br>
$text = "I like banana and orange juice.";</p>
<p>$found = false;<br>
foreach ($keywords as $word) {<br>
if (stristr($text, $word) !== false) {<br>
$found = $word;<br>
break;<br>
}<br>
}</p>
<p>if ($found !== false) {<br>
echo "Found keyword: $found\n";<br>
} else {<br>
echo "No keywords found.\n";<br>
}</p>
<p>/**</p>
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<p>4. Summary</p>
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<p>The second parameter of stristr must be a string; arrays are not allowed directly.</p>
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<p>For multi-keyword matching, loop through an array and call stristr for each keyword.</p>
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<p>This allows flexible checking if a string contains any of multiple keywords.</p>
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<p>Related functions</p>
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<p>stripos: Case-insensitive search for string position, second parameter is also a string.</p>
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<p>preg_match: Can also use regex for multi-keyword matching, e.g., pattern /(apple|banana|orange)/i.</p>
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<p data-is-last-node="">The above provides a detailed explanation and example of using stristr's second parameter and the differences between strings and arrays.<br>
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