How to traverse a two-dimensional array in php

PHP is a popular server-side scripting language that is often used in website development and application development. In PHP applications, two-dimensional arrays are often used because they can save complex data structures, such as tables, and are also very useful for large-scale data processing.

Traversing a two-dimensional array is a relatively basic operation. This article will introduce several methods of traversing a two-dimensional array in PHP.

1. Use for loop

Using for loop is the most basic way to traverse an array. It traverses a two-dimensional array through two layers of for loops.

$array = array(
     array("John", "Smith", 31),
     array("Jane", "Doe", 23),
     array("Mike", "Jones", 26)
);

for ($row = 0; $row < 3; $row++) {
      echo "<p><b>Row number $row</b></p>";
      echo "<ul>";
      for ($col = 0; $col < 3; $col++) {
           echo "<li>".$array[$row][$col]."</li>";
      }
      echo "</ul>";
}

The above code will output the following content:

Row number 0
- John
- Smith
- 31

Row number 1
- Jane
- Doe
- 23

Row number 2
- Mike
- Jones
- 26

Through the for loop, we can output each element according to the subscript of the two-dimensional array.

2. Use foreach loop

The foreach loop is a more advanced way to traverse an array. It will automatically assign each element in the array to a variable to facilitate reading data.

$array = array(
     array("John", "Smith", 31),
     array("Jane", "Doe", 23),
     array("Mike", "Jones", 26)
);

foreach ($array as $row) {
      echo "<p><b>Row</b></p>";
      echo "<ul>";
      foreach ($row as $value) {
           echo "<li>".$value."</li>";
      }
      echo "</ul>";
}

The above code will output the following:

Row
- John
- Smith
- 31

Row
- Jane
- Doe
- 23

Row
- Mike
- Jones
- 26

As you can see, it is easier to read each element in the array using a foreach loop, and the code is more concise.

3. Use the array_map function

The array_map function can operate on arrays, including traversing two-dimensional arrays. We can use the array_map function to iterate through each element of a two-dimensional array and output them to HTML.

$array = array(
     array("John", "Smith", 31),
     array("Jane", "Doe", 23),
     array("Mike", "Jones", 26)
);

function printRow($row) {
      echo "<p><b>Row</b></p>";
      echo "<ul>";
      array_map(function($value) {
            echo "<li>".$value."</li>";
      }, $row);
      echo "</ul>";
}

array_map("printRow", $array);

The above code will output the following:

Row
- John
- Smith
- 31

Row
- Jane
- Doe
- 23

Row
- Mike
- Jones
- 26

4. Using the array_walk function

The array_walk function allows us to execute a callback function to traverse the array. We can use this to iterate over 2D arrays and output them to HTML.

$array = array(
     array("John", "Smith", 31),
     array("Jane", "Doe", 23),
     array("Mike", "Jones", 26)
);

function printRow($row) {
      echo "<p><b>Row</b></p>";
      echo "<ul>";
      array_walk($row, function($value) {
            echo "<li>".$value."</li>";
      });
      echo "</ul>";
}

array_walk($array, "printRow");

The above code will output the following:

Row
- John
- Smith
- 31

Row
- Jane
- Doe
- 23

Row
- Mike
- Jones
- 26

Using the array_walk function to traverse a two-dimensional array is more concise, and there is no need to use loops in the code.

Summary

Traversing a two-dimensional array is a common operation in PHP development. It is very useful for us to deal with complex data structures. This article introduces several methods of traversing two-dimensional arrays, including for loop, foreach loop, array_map function and array_walk function. You can choose a suitable method to operate two-dimensional arrays according to your needs.

The above is the detailed content of How to traverse a two-dimensional array in php. For more information, please follow other related articles on the PHP Chinese website!