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! */ } |
