Re: Watch out for automatic type casting

On 29 Mar 2012, at 17:57, Arno Kuhl wrote: > I found automatic typecasting can be a bit of a gotcha. > > > > $sText = "this.is.a.test.text"; > > if ( $pos = strpos($sText, "test") !== FALSE) { > > echo substr($sText, 0, $pos)."<".substr($sText, $pos, > strlen("test")).">".substr($sText, $pos+strlen("test")); > > } > > > > The code seems logical enough, and the expected result would be: > > this.is.a.<test>.text > > > > In fact it ends up being: > > t<his.>is.a.test.text > > > > The reason is $pos is typecast as TRUE, not int 10, presumably because it's > in the same scope as the boolean test. > > Then when $pos is later used as an int it's converted from TRUE to 1. > > > > You have to bracket the $pos setting to move it into its own scope to > prevent it being typecast: > > if ( ($pos = strpos($sText, "test")) !== FALSE) { > > > > No doubt it's mentioned somewhere in the php manual, I just never came > across it. > > Just thought I'd highlight one of the gotchas of auto typecasting for any > other simpletons like me. This is not due to typecasting, it's due to operator precedence. In PHP (and many other languages) the !== comparison operator will get done first, so the result of that comparison will be assigned to $pos. By introducing the brackets you're explicitly specifying the order. Details here: http://php.net/operators.precedence -Stuart -- Stuart Dallas 3ft9 Ltd http://3ft9.com/