My favorite PHP gotchas

PDO.php

<?php

// https://bugs.php.net/bug.php?id=53567

function create_pdo()
{
    return new PDO("mysql:host=localhost;dbname=test",
                   "test", "my_password",
                   array(PDO::ATTR_PERSISTENT => true));
}

$pdo1 = create_pdo();
$pdo2 = create_pdo();

$pdo1->query("SELECT i_can_has_fail() ;");
var_dump($pdo2->errorInfo());

?>

sort.php

<?php

function dump($var)
{
    return str_replace("\n", "", var_export($var, true));
}

echo "Sorting a mixed type array (manual does warn about issues):\n\n";

$array = array("1", 1, "a");
echo "  Unsorted array: " . dump($array) . "\n";

sort($array);
echo "  After sorting:  " . dump($array) . "\n";

sort($array);
echo "  Sorting again:  " . dump($array) . "\n";


echo "\nSorting a non-mixed type array (should be safe):\n\n";

$array = array("a", "2", "3e-1");
echo "  Unsorted array:    " . dump($array) . "\n";

sort($array);
echo "  \"Regular\" sorting: " . dump($array) . "\n";

sort($array, SORT_NUMERIC);
echo "  Numerical:         " . dump($array) . "\n";

sort($array, SORT_STRING);
echo "  As strings:        " . dump($array) . "\n";

?>

string_equality.php

<?php

function print_equality($a, $b)
{
    $repr_a = var_export($a, true);
    $repr_b = var_export($b, true);
    echo "$repr_a == $repr_b is ";
    var_dump($a == $b);
}

print_equality("42", "042");
print_equality("4.2e1", "042");
print_equality("0xE", "0Xe");
print_equality("0E999", "42e-4242");

?>

strpos.php

<?php

error_reporting(E_ALL);

function print_strpos($haystack, $needle)
{
    $repr_haystack = var_export($haystack, true);
    $repr_needle = var_export($needle, true);
    echo "Find needle=$repr_needle in haystack=$repr_haystack: ";
    var_dump(strpos($haystack, $needle));
}

print_strpos("hello", "hell");
print_strpos("", "world");
print_strpos(false, null);
print_strpos("world", "");
print_strpos("", "");

?>

substr.php

<?php

var_dump(substr("hello", 0, 0));
var_dump(substr("", 0, 0));

?>