PHP Loops

Loops in PHP: while, do-while, for, & foreach

Loops repeat a block of code as long as a specified condition remains true. PHP supports 4 primary loop types suited for numeric iterations, condition-driven loops, and array traversals.

Loop Types Comparison

flowchart TD
    A["Choose Loop Type"] --> B{"Is Iterating Over Array / Collection?"}
    B -- Yes --> C["foreach ($items as $key => $val)"]
    B -- No --> D{"Known Fixed Iteration Count?"}
    D -- Yes --> E["for ($i = 0; $i < $count; $i++)"]
    D -- No --> F{"Execute At Least Once?"}
    F -- Yes --> G["do { ... } while (condition);"]
    F -- No --> H["while (condition) { ... }"]

Loop Interruptions: break & continue

• break: Exits loop immediately.
• continue: Skips current iteration step and proceeds to next iteration loop evaluation.

Practical Code Example

<?php
declare(strict_types=1);

// 1. foreach Loop with Key & Value
$userRoles = [
    'maksudur' => 'Administrator',
    'sarah' => 'Senior Developer',
    'john' => 'Project Manager'
];

echo "--- User Role Directory ---
";
foreach ($userRoles as $username => $role) {
    echo "User: " . ucfirst($username) . " | Role: " . $role . "
";
}

// 2. for Loop with step and break/continue logic
echo "
--- Evens Only (Break at 8) ---
";
for ($i = 1; $i <= 10; $i++) {
    if ($i % 2 !== 0) {
        continue; // Skip odd numbers
    }
    if ($i == 8) {
        break; // Interrupt loop at 8
    }
    echo "Even Count: $i
";
}

// 3. while Loop for Process Polling
$attempts = 0;
while ($attempts < 3) {
    $attempts++;
    echo "Attempting Connection #$attempts...
";
}

Best Practices

• Use foreach for All Array Iterations: foreach is optimized, readable, and prevents array out-of-bounds indexing errors.
• Avoid Modifying Array Elements Inside foreach Without Reference: Use foreach ($array as &$value) if mutating values directly, and call unset($value) immediately after.
• Avoid Heavy Calculations Inside for Loop Headers: Write $len = count($arr); for ($i=0; $i < $len; $i++) instead of calling count() on every iteration step.

Self-Check Challenge

Write a foreach loop over an associative array $prices = ['laptop' => 1200, 'mouse' => 25, 'desk' => 300] that prints items costing more than $50!