php数组判断键值是否存在示例

/*
 
array_key_exists() 在给定的 key 存在于数组中时返回 TRUE。key 可以是任何能作为数组索引的值。
 
*/
 
$search_array = array("first" => 1, "second" => 4);
if (array_key_exists("first", $search_array)) {
   echo "The 'first' element is in the array";
}
?>

$a = array('a'=>1, 'b'=>0, 'c'=>NULL);
 
echo 'a test by empty: ' , empty($a['a']) ? 'not exist' : 'exist', PHP_EOL;
echo 'a test by isset: ' , isset($a['a']) ? 'exist' : 'not exist', PHP_EOL;
echo 'a test by array_key_exists: ' , array_key_exists('a', $a) ? 'exist' : 'not exist', PHP_EOL, PHP_EOL;
 
echo 'b test by empty: ' , empty($a['b']) ? 'not exist' : 'exist', PHP_EOL;
echo 'b test by isset: ' , isset($a['b']) ? 'exist' : 'not exist', PHP_EOL;
echo 'b test by array_key_exists: ' , array_key_exists('b', $a) ? 'exist' : 'not exist', PHP_EOL, PHP_EOL;
 
echo 'c test by empty: ' , empty($a['c']) ? 'not exist' : 'exist', PHP_EOL;
echo 'c test by isset: ' , isset($a['c']) ? 'exist' : 'not exist', PHP_EOL;
echo 'c test by array_key_exists: ' , array_key_exists('c', $a) ? 'exist' : 'not exist', PHP_EOL, PHP_EOL;

输出结果如下：

========================================================

a test by empty: exist

a test by isset: exist

a test by array_key_exists: exist

b test by empty: not exist

b test by isset: exist

b test by array_key_exists: exist

 
c test by empty: not exist

c test by isset: not exist

c test by array_key_exists: exist