How to break an outer loop with PHP ?

In PHP, breaking an outer loop refers to exiting a parent loop from within a nested loop. This can be achieved using the break statement with a numeric argument indicating how many levels of loops to exit. It helps control complex loop flow efficiently.

Using break keyword

In PHP, the break keyword immediately terminates a loop, resuming program execution at the next statement. In nested loops, you can pass a numeric argument to `break` to exit multiple loops, controlling the flow of complex structures efficiently.

Syntax

break number_of_nested_loop_to_terminate;

Parameters: The break keyword followed by a numeric argument which is by default 1. Passing of variables and 0 as a numeric argument is not allowed.

Examples:

break 2; // It terminates second outer loop
break 3; // It terminates third outer loop
break $num; // Variable cannot be used as numeric argument since version 5.4.0
break 0; // 0 is not a valid argument to pass

Below programs illustrate how to break outer loops in PHP:

Example : In this example we demonstrates the use of the break statement with an argument of 2 to exit both the inner while loop and the outer for loop when a specific condition is met.

<?php

// Initialize a number
$num = 10;

// Outer loop to iterate $num times
for( $i = 0; $i < 10; $i++ ) {
    
    // Initialize a variable $j
    $j = 1;
    
    // Inner loop
    while( $j <= 3 ) {
        
        if( $i >= 1 )
        
            // Breaking the outer loop
            break 2;
            
        echo $j . " ";
        $j++;
    } 
}

?>

1 2 3

Example: In this example we searches for a number in a 2D array using nested loops. It uses break 2 to exit both loops when the number is found, ensuring efficient execution.

<?php

// Create a 2D array
$arr = array(
    array (105, 96, 112), 
    array(96, 45, 63) 
);

// Initialize a number which
// need to fine in the array
$num = 45;

// Declare a boolean variable and
// initialize it with false
$found = FALSE;

// Outer loop
for($i = 0; $i < 2; $i++) {
    
    // Inner loop
    for($j = 0; $j < 3; $j++) {
        
        if($num == $arr[$i][$j]) {
            $found = TRUE;
            
            // Terminate the outer loop
            break 2;
        }
    } 
}

// Check number is found or not
if( $found )
    echo $num . " is found in the array";
else
    echo $num . " is not found in the given array";

?>

45 is found in the array

Using goto keyword

The goto keyword in PHP allows jumping to a specific label, bypassing normal flow control. It can be used to break out of nested loops by directing execution to a labeled statement, though its use is generally discouraged due to reduced code readability.

Example : In this example we searches for a number in a 2D array and uses the goto keyword to exit both loops when the number is found, improving loop termination efficiency.

<?php

// Create a 2D array
$arr = array(
    array (105, 96, 112), 
    array(96, 45, 63) 
);

// Initialize a number which
// need to fine in the array
$num = 45;

// Declare a boolean variable and
// initialize it with false
$found = FALSE;

// Outer loop
for($i = 0; $i < 2; $i++) {
    
    // Inner loop
    for($j = 0; $j < 3; $j++) {
        
        if($num == $arr[$i][$j]) {
            $found = TRUE;
            
            // Terminate the outer loop
            // using goto keyword
            goto terminateLoop;
        }
    } 
}

// target label
terminateLoop:

// Check number is found or not
if( $found )
    echo $num . " is found in the array";
else
    echo $num . " is not found in the given array";

?>

45 is found in the array