Question

I have a string like this: $str1 = "mod 1 + mode 2 + comp 1 + toto".

I would like to test if mod 1 is in $str1. I used strpos but this function doesn’t help.

Answer 1

strpos returns the position of the occurrence in the string starting with 0 or false otherwise. Using just a boolean conversion like in the following is a common mistake:

$str1 = "mod 1 + mode 2 + comp 1 + toto";
if (strpos($str, "mod 1")) {
    // found
}

Because in this case strpos will return 0. But 0 converted to Boolean is false:

var_dump((bool) 0 === false);  // bool(true)

So you need to use a strict comparison:

$str1 = "mod 1 + mode 2 + comp 1 + toto";
if (strpos($str, "mod 1") !== false) {
    // found
}

This is also what the documentation advises:

Warning This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE, such as 0 or “”. Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.