PHP quirks and pitfalls [closed]

Answer 1

I hate how you can get issues if you close php files with a ?> closing tag (which seems like it should be the other way around). For example, include a file with some whitespace after the ?> and then try to change headers (assuming no output buffering). UGH. Took me way to long to learn to never close php files with ?>

Answer 2

== EDIT == This is no longer true for PHP >= 5.5!

What I sometimes run into is the Fatal error: Can't use function return value in write context error when using the empty() construct. For example:

if (!empty(trim($_GET['s']))) {
    // ...
}

empty() needs a variable, anything else will result in the error.

The solution:

$s = trim($_GET['s']);
if (!empty($s)) {
    // ...
}

Answer 3

$x = "a string";

if ($x == 142)
{
    echo "lol, of course $x is a number";
}
else
{
    echo "$x is clearly not equal to 142";
}

When run:

lol, of course a string is a number

You must use ===

$x = "a string";

if ($x === 142)
{
    echo "lol, of course $x is a number";
}
else
{
    echo "$x is clearly not equal to 142";
}

When run:

a string is clearly not equal to 142

Answer 4

I've had all sorts of bother combining foreach with references

$testarray = array(1 => "one", 2 => "two");
$item = "three";
$testarray[3] =& $item;
foreach ($testarray as $key => $item) {
  // do nothing
}
echo $testarray[3]; // outputs "two"

This really threw me off during the PHP4 era, and although it's gotten better in PHP5 by having sane behavior if you don't use explicit references, I still manage to get caught by this one now and then.

Answer 5

my favorite:

<?php
$a = 0;
$b = 'x';
var_dump(FALSE == $a);
var_dump($a == $b);
var_dump($b == TRUE);

echo' <br />Conclusion: TRUE equals FALSE (at least in PHP)';

Answer 6

Having functions behave differently on different OS'es, and some functions are available only on specific OS'es.

For example, the mail() function on Windows cannot take sender name in the $to parameter. It can only contain email address. On Linux all works fine.

Another example, the function strptime() is only available on Linux, and not Windows (this got me in an existing project I wanted to run on my Windows box).

Sure, there are some functions that make sense only on certain OS'es (like Win32API functions), but many others seem like they should behave the same on all OS'es, when in fact they do not.