I've no certainty here, but I strongly suspect that it's a Perlism that PHP partially took.
In Perl, $a == $b would be true -- just like in PHP. However, in Perl, you use string comparison ($a eq $b) when you want to compare strings. PHP doesn't seem to have string comparison outside of ==.
As a CFML developer who has had to bear the brunt of gleeful derision, you won't get an apology from me. :-)
Modern CFML running on Railo is an awesome environment to work in: PHP-like hackability, a very consistent language spec, native JVM performance, first-class java library integration, and it's a 100% pure open source software stack.
Whereas PHP has a much slower runtime, a horrific language spec, and nothing similar to the benefit of running on a common runtime like the JVM.
In Perl, $a == $b would be true -- just like in PHP. However, in Perl, you use string comparison ($a eq $b) when you want to compare strings. PHP doesn't seem to have string comparison outside of ==.