PHP comparison among strings in different php servers - php

Question

I have an php in a server and i found an issue (solved). The issue was in a comparison among to long integer saved in a string and I can not use Equal, I have to use Identical. But I do not know why I have to use it, if it is a comparison among to strings.
I make a test, and I get two different results, in local host and server.
Server PHP version: 5.3.10-1ubuntu3.10
Local PHP version: 5.6.30-7+deb.sury.org~xenial+1
Here is mi code:
<?php
$a = "1285615000003961035";
$b = "1285615000003961023";
if($a == $b)
{
echo "$a == $b<br>";
}
else
{
echo "$a != $b<br>";
}
if((string)$a == (string)$b)
{
echo "(string)" . (string)$a . " == (string)" . (string)$b . "<br>";
}
else
{
echo "(string)" . (string)$a . " != (string)" . (string)$b . "<br>";
}
if($a === $b)
{
echo "$a === $b<br>";
}
else
{
echo "$a !== $b<br>";
}
if((string)$a === (string)$b)
{
echo "(string)" . (string)$a . " === (string)" . (string)$b . "<br>";
}
else
{
echo "(string)" . (string)$a . " !== (string)" . (string)$b . "<br>";
}
?>
In Server I get:
1285615000003961035 == 1285615000003961023
(string)1285615000003961035 == (string)1285615000003961023
1285615000003961035 !== 1285615000003961023
(string)1285615000003961035 !== (string)1285615000003961023
and in local:
1285615000003961035 != 1285615000003961023
(string)1285615000003961035 != (string)1285615000003961023
1285615000003961035 !== 1285615000003961023
(string)1285615000003961035 !== (string)1285615000003961023

Answer 1

Since PHP 5.4, according to the release notes, integral strings that overflow into floating point numbers will no longer be considered equal, because of the way float numbers are represented internally.
For more information see the links below:
http://php.net/manual/en/language.operators.comparison.php (Warning section after the examples)
http://php.net/manual/en/types.comparisons.php#108264

Answer 2

You should use strcmp or === for comparing strings (as you have used), because when you use == PHP will do type conversions.
http://php.net/manual/en/language.operators.comparison.php
Edit: As Lucas Mendes stated above, this is only partially true after PHP 5.4 - but still it is safer to use operators that do not do type conversions by default to compare strings.