Tag Archives: Tips

PHP: isset () vs strlen ()

How to test the length of a string in PHP ?  Well, PHP has a function called strlen () for this purpose.
So obviously, a simple if (strlen ($str) > 10) { ... } should do the trick, isn’t it?

Actually, there’s another way to do that: considering that a string is an array of characters, it’s possible to test if a character is set at the length we want to check with isset (). So the line of code above should be replace by if (isset ($str [10]) { ... }.

Why should we use isset () instead of strlen ()?

Well, it’s way faster: running the test above 100 000 times for each function gives me:
strlen () : 0.034812927246094 seconds
isset () : 0.0079290866851807 seconds

PHP: isset()

isset() is a function testing if a variable $var is set or not.

boolean isset (mixed $var[, mixed $var[,...]])

It returns TRUE is the variable is set, and FALSE if it isn’t.

Using isset() for testing a variable saves some times compared to try to use an nonexistent one. It also helps to avoid error messages from PHP:

/* The line below generates the warning message:
* Notice: Undefined variable: var in /path/to/script.php on line 1
$toto = $var;

/* Of course it's possible to silence with @ the warnings from PHP but it's costly */
$toto = @$var;

/* Do this instead: */
if (isset ($var)) {
$toto = $var;

As seen in the function definition above, isset can take multiple arguments. But it is faster to have an if statement with one isset() call per variable rather than one isset() call with several variables:

if (isset($a) && isset($b)) { } /* Fast */

if (isset($a, $b)) { } /* Slow */