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Returning Failure in PHP
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Returning Failure in PHP

InfinityCoder November 23, 2016

You want to indicate failure from a function.

Return false:

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function lookup($name) {
   if (empty($name)) { return false; }
   /* ... */
}
 
$name = 'alice';
 
if (false !== lookup($name)) {
    /* act upon lookup */
} else {
    /* log an error */
}

In PHP, nontrue values aren’t standardized and can easily cause errors. As a result, your functions should return the defined false keyword because this works best when checking a logical value.
Other possibilities are ” or 0. However, while all three evaluate to nontrue inside an if, there’s actually a difference among them.

Also, sometimes a return value of 0 is a meaningful result, but you still want to be able to also return failure.
For example, strpos() returns the location of the first substring within a string. If the substring isn’t found, strpos() returns false. If it is found, it returns an integer with the position.

Therefore, to find a substring position, you might write:

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if (strpos($string, $substring)) { /* found it! */ }

However, if $substring is found at the exact start of $string, the value returned is 0. Unfortunately, inside the if, this evaluates to false, so the conditional is not executed.

Here’s the correct way to handle the return value of strpos():

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if (false !== strpos($string, $substring)) { /* found it! */ }

 

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