CODEWITHSUNDEEP
php
reignsly
reignsly

Reputation: 502

PHP : confused with "==" operator

Can somebody explain to me why this codes returns "TRUE". I know that i should use the "===" rather "==" but I run to this code and wondering why it returns to true. Thanks in advance.

<?php
    $s = "final";
    $i = 0;
    if($s == $i){
        echo "TRUE";
    }else{
        echo "FALSE";
    }

Upvotes: 0

Views: 122

Answers (5)

xlecoustillier
xlecoustillier

Reputation: 16351

Take a look at the PHP comparison tables.

You can see in the "Loose comparisons with ==" table that comparing the number 0 with a string containing text ("php" in the example) evaluates to TRUE.

Upvotes: 1

Zudwa
Zudwa

Reputation: 1400

From PHP comparison operators:

If you compare a number with a string or the comparison involves numerical strings, then each string is converted to a number and the comparison performed numerically.

And from PHP string conversion to numbers:

The value is given by the initial portion of the string. If the string starts with valid numeric data, this will be the value used. Otherwise, the value will be 0 (zero).

So when you compare integer and a string, PHP tries to convert string to integer first and as "final" doesn't contain any valid numeric data, it is converted to 0.

You can try:

var_dump( intval('12final') );      //int(12)
var_dump( floatval('1.2final') );   //float(1.2)

This is because of both 12final and 1.2final start with valid numeric data (12 and 1.2 respecrively), their converted value is not 0.

Upvotes: 1

user3816703
user3816703

Reputation: 129

As mentionned above, it is an issue with php's loose comparison. The accepted answer on php string comparasion to 0 integer returns true? Explains it well enough IMHO. in short "==" attempts to cast your string into an int, and since it fails, the resulting int has a value of 0

Upvotes: 1

Efog
Efog

Reputation: 1179

When you are trying to compare string and number, interpretator converts your string to int, so you got 0 == 0 at final. Thats why string == 0 is true.

Upvotes: 5

Allmighty
Allmighty

Reputation: 1519

This is just a property of the loose comparisons implemented in PHP. I wouldn't search for any more logic behind this than that this is a given.

Upvotes: 1

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