PHP strpos($a, $b) >= 0 is true even when $b is not in $a

Question

After reading How do I check if a string contains a specific word in PHP? and the documentation about strpos() at http://php.net/manual/en/function.strpos.php, I try an alternative of the first link, instead of !==, I use >= 0

$a = "Hello";
$b = "a";
if(strpos($a, $b) >= 0) {
  echo 'string found';
} else {
  echo 'string not found';
}

prints 'string found' and not 'string not found'? $b is obviously not in $a, so strpos() should return false, hence it should enter the else, what's going on here?

`>=` 0 is not an alternative of `!==`. It is in this context close to `!=`, which is totally different from `!==`. — eis, Nov 23 '12 at 08:15
possible duplicate of [PHP - How to check if a string contain specific words](http://stackoverflow.com/questions/4366730/php-how-to-check-if-a-string-contain-specific-words) — tereško, Nov 23 '12 at 23:58

score 2 · Answer 1 · edited Nov 23 '12 at 08:19

2

In that case, strpos did return false. However, any value other than 0 is treated as true in php, including negatives that is, and 0 is treated as false. So,

if(strpos($a, $b) >= 0)

is evaluated into

if(false >= 0)

and then

if(0 >= 0)

which is true

You should use !== false instead, so if(strpos($a, $b) !== false)

edited Nov 23 '12 at 08:19

Alain Tiemblo

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answered Nov 23 '12 at 08:11

絢瀬絵里

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1

There is no `>==` operator in PHP. Read: http://www.php.net/manual/en/language.operators.comparison.php – eisberg Nov 23 '12 at 08:15
I did http://codepad.org/AjUOVKuX and it did: Parse error: syntax error, unexpected '=' on line 2 – eisberg Nov 23 '12 at 08:18
Replaced by `!== false` instead. – Alain Tiemblo Nov 23 '12 at 08:19

score 1 · Answer 2 · answered Nov 23 '12 at 08:17

Please read the manual: php.net/manual/en/function.strpos.php

You will notice that strpos will return false is $b is not in $a. You will need to check it this way:

<?php
$a = "Hello";
$b = "a";
if(strpos($a, $b) !== false) {
  echo 'string found';
} else {
  echo 'string not found';
}

score 0 · Answer 3 · answered Nov 23 '12 at 08:27

0

if(strpos($a, $b) >= 0) 
strpos($a, $b) returns false
if(false >= 0) is true.

Here we need to check type.

answered Nov 23 '12 at 08:27

som

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PHP strpos($a, $b) >= 0 is true even when $b is not in $a

3 Answers3