php检查指定的键名是否存在于数组中的函数array_key_exists()

<?php
$a=array("Volvo"=>"XC90","BMW"=>"X5");
if (array_key_exists("Volvo",$a))
{
echo "Key exists!";
}
else
{
echo "Key does not exist!";
}
?>

array_key_exists(key,array)

<?php
$a=array("Volvo"=>"XC90","BMW"=>"X5");
if (key_exists("Toyota",$a))
{
echo "Key exists!";
}
else
{
echo "Key does not exist!";
}
?>

<?php
$a=array("Volvo","BMW");
if (array_key_exists(0,$a))
{
echo "Key exists!";
}
else
{
echo "Key does not exist!";
}
?>

<?php 
$a=array("a"=>"Dog","b"=>"Cat"); 
if (array_key_exists("a",$a)) 
{ 
echo "Key exists!"; 
} 
else 
{ 
echo "Key does not exist!"; 
} 
?>

<?php 
$a=array("a"=>"Dog","b"=>"Cat"); 
if (array_key_exists("c",$a)) 
{ 
echo "Key exists!"; 
} 
else 
{ 
echo "Key does not exist!"; 
} 
?>

Key does not exist!

<?php 
$a=array("Dog",Cat"); 
if (array_key_exists(0,$a)) 
{ 
echo "Key exists!"; 
} 
else 
{ 
echo "Key does not exist!"; 
} 
?>