Detailed explanation and example code of using PHP foreach loop_PHP tutorial

The basic syntax of foreach is as follows:
FOREACH ($array_variable as $value)
{
[code to execute]
}
or
FOREACH ($array_variable as $key => $value)
{
[code to execute]
}
In both cases, multiple [code to execute] will be executed that is equal to the array element in $array_variable number.
Let’s look at an example. Suppose we have the following code snippet:

Copy code The code is as follows:

$array1 = array(1,2,3 ,4,5);
FOREACH ($array1 as $abc)
{
print "new value is " . $abc*10 . "
";
}

Output result
new value is 10
new value is 20
new value is 30
new value is 40
new value is 50
foreach loop above experience All 5 elements of the array $array1 are printed out each time in a statement containing 10 times the value of the array element.
The function of foreach is to iterate through all the values ​​​​of the current array and assign them to $var
Official example code:

Copy code The code is as follows :

/* foreach example 1: value only */
$a = array(1, 2, 3, 17);
foreach ($ a as $v) {
echo "Current value of $a: $v.n";
}
/* foreach example 2: value (with key printed for illustration) */
$a = array(1, 2, 3, 17);
$i = 0; /* for illustrative purposes only */
foreach ($a as $v) {
echo "$a[$i] => $v.n";
$i++;
}
/* foreach example 3: key and value */
$a = array(
"one" => 1,
"two" => 2,
"three" => 3,
"seventeen" => 17
);
foreach ($a as $k => $v) {
echo "$a[$k] => $v.n";
}
/* foreach example 4: multi-dimensional arrays */
$a = array() ;
$a[0][0] = "a";
$a[0][1] = "b";
$a[1][0] = "y";
$a[1][1] = "z";
foreach ($a as $v1) {
foreach ($v1 as $v2) {
echo "$v2n";
}
}
/* foreach example 5: dynamic arrays */
foreach (array(1, 2, 3, 4, 5) as $v) {
echo "$vn";
}
?>

Let’s look at an example of foreach operating on multidimensional data

Copy the code The code is as follows :

$s = array(array(1,2),array(3,4),array(5,6));
foreach( $s as $v => $_v )
{
foreach( $_v as $vc => $_vc )
{
echo $_vc[0],'|'.$_vc[1],'< br /> >
Copy code

The code is as follows:

foreach ($array as $key=>$value)
{

…… } For ease of understanding, we assume that $array here is a one-dimensional related array, $key is the index of the array, $value is the value of this index, and their names can be arbitrary. They are called $key and $value for ease of understanding. In order to allow you to better understand the working process of foreach, let's create an array:

$array = array('first'=>'ibm','second'=>'hp');

Now we simulate the PHP service to use foreach to traverse $array:



Copy code

The code is as follows:


foreach ($array as $key=>$value)
{

echo $key.'=>'.$value; }
The first loop, $key = 'first', $value = 'ibm', at this time, foreach actually performs an invisible operation on $array: next($array), moving the array pointer forward (The "forward" here is the same as in the PHP manual, not what we usually understand as "forward") Move one. Then the echo statement outputs "first=>ibm".
In the second loop, it will first determine whether the current pointer of the array $array has reached the end of the array. If so, end the loop, otherwise it will enter the second loop. Of course, such a judgment will also occur when entering the first loop. If $array is an empty array, then the statements below the loop will be executed directly. At this time, $key = 'second', 'value' = 'hp', and after next($array), "second=>hp" is output. Then it is judged that the array pointer has reached the end and the following statement is executed.
By now you should have some understanding of the foreach loop, right? Another thing to note is that foreach only passes a value each time, rather than actually operating on the array elements. Specific to the above example, if you want to add the string 'company' after each array element, then the operation $value .= 'company' will not work. It will not change the value of the array element. At this time you should use it like this: $array[$key] .= 'company';

For more information, please refer to: php foreach
php foreach, while performance comparison
php loop

http://www.bkjia.com/PHPjc/321830.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/321830.htmlTechArticleThe basic syntax of foreach is as follows: FOREACH ($array_variable as $value) { [code to execute] } or FOREACH ($ array_variable as $key = $value) { [code to execute] } In both cases, more...