_php tutorial for iterating through array methods in PHP

There are several implementations of traversing an array:

1. An array of contiguous indexes:

The traversal of a contiguous array is simple, because the index of the array is continuous (0 1 2 ...), so we can first use the count () function to calculate the number of elements in the arrays, and then create a for loop, as follows:

$subject =array ("Maths", "中文版", "Physics");

$num _elements=count ($subject); At this point the value of $num_elements is 3

for ($i =0; $i < $num _elements; + + $i) {

Echo ("$subject [$i]

n ");

}

The result is:

Maths

中文版

Physics

Here we give $i an initial value of 0, because the index of the array element defaults to 0 1 2, if the first element's index is not 0, we just need:

$subject =array (3=> "maths", "中文版", "Physics");

$num _elements=count ($subject) +3; Watch this.

for ($i =3; $i < $num _elements; + + $i) {

Echo ("$subject [$i]

n ");

}

Here the $i is assigned a value of 3, while $num_elements=count ($subject) +3, which is easily overlooked.

2. An array of non-contiguous indexes:

$subject =array ("M" = "maths", "e" = "English", "P" and "Physics");

An array is created here, with the index values "M", "E" "P", respectively, how do the arrays traverse?

Method One: Use the list () and each () function combination

$subject =array ("M" = "maths", "e" = "English", "P" and "Physics");

Reset ($subject); Reset the pointer to the first element

while (list ($key, $value) =each ($subject)) {

echo "$key is $value

n "; }

Method Two: Using the foreach statement

$subject =array ("M" = "maths", "e" = "English", "P" and "Physics");

foreach ($subject as $key = = $value) {

echo "$key is $value

n ";

}

?>

is not simpler than list () and each ().

The difference between the foreach and list () each () combination:

foreach performs operations on a copy of the original array. His advantage is that it does not affect the position of the current array pointer, and the disadvantage is that it takes a long time to replicate for a large array.

The list () each () combination is obviously used to traverse, and then the position of the pointer changes.

Method Three: Use the Array_walk () function to iterate over an array

Array_walk () is a user-defined function that handles every element in the array.

$subject =array ("Maths", "中文版", "Physics");

function Printelement ($element) {

Print ("$element

n ");

}

Array_walk ($subject, "printelement");

The above is to help the home network for you to introduce the traversal array method in PHP, I hope to help you.

http://www.bkjia.com/PHPjc/371793.html www.bkjia.com true http://www.bkjia.com/PHPjc/371793.html techarticle There are several ways to iterate through an array: 1, an array of contiguous indexes, it is simple to implement a continuous array, because the index of the array is continuous (0 1 2), so we can start with count ...

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