Search code examples
phpstringstrcmp

PHP strcmp result int meaning

In php, there is a built-in function strcmp to compare if two strings are same or not.

Returning value is integer number that if the first parameter is greater than the second I get > 0, if not < 0 and if the same 0.

So the part I don't get is comparing string as number. Does PHP convert string to number and if so how's PHP converting?

$a = 'acorn';
$b = 'zebra';
var_dump( strcmp($a, $b) ); // -25 <- what's this number? seems like alphabetical position...nnn

Doesn't it really matter what number I get, shall I just take what it is?

Solution

  • Looking at the PHP: strcmp doc :

    Returns < 0 if str1 is less than str2; > 0 if str1 is greater than str2, and 0 if they are equal.

    So yes, you can use it as it is to compare your string.

    But if you want to understand the number returned by the function, it depend on the characters that makes the strings.

    In ASCII :

    A=65 < B=66 < C=67 ....

    So if the string are different, one is gonna be greater than the other.

    So you can also test it easily with a short script :

    <?php

$a='A';
$b='B';
$c='C';

//Return -1 because $a is smaller than $b by one (65 < 66 )
echo strcmp($a,$b);

//Return -2 because $a is smaller than $c by two (65 < 67 )
echo strcmp($a,$c);


//Return -1 because $b is smaller than $c by one (66 < 67 )
echo strcmp($b,$c);

//Return 1 because $c is greater than $b by one (67 > 66 )
echo strcmp($c,$b);

//Return 2 because $c is greater than $a by two (67 > 65 )
echo strcmp($c,$a);