PHP में Key के आधार पर Array Element Delete करना

PHP में array से specific key के आधार पर element remove करने के तरीके।

विधि 1: unset() - Basic Removal

<?php
$arr = ['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4];

unset($arr['b']); // Key 'b' remove करें

print_r($arr);
// Array ( [a] => 1 [c] => 3 [d] => 4 )
// Keys preserved: a, c, d (no re-index for associative)

विधि 2: array_diff_key() - Multiple Keys Remove

<?php
$arr = ['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5];
$keysToRemove = ['b', 'd'];

// Flip keys to use as filter
$filter = array_flip($keysToRemove); // ['b' => 0, 'd' => 0]

$result = array_diff_key($arr, $filter);

print_r($result);
// Array ( [a] => 1 [c] => 3 [e] => 5 )

विधि 3: array_filter() - Condition-based Removal

<?php
$arr = ['apple' => 1, 'banana' => 2, 'cherry' => 3, 'date' => 4];

// Keys starting with 'a' या 'c' remove करें
$filtered = array_filter($arr, function($value, $key) {
    return !in_array($key[0], ['a', 'c']); // Keep if not a or c
}, ARRAY_FILTER_USE_BOTH);

print_r($filtered);
// Array ( [banana] => 2 [date] => 4 )

विधि 4: Numeric Arrays - Re-indexing के साथ

<?php
$arr = ['John', 'Jacob', 'Tom', 'Tim']; // Keys: 0, 1, 2, 3

// Index 1 remove करें और re-index
unset($arr[1]);
$arr = array_values($arr); // Re-index to 0, 1, 2

print_r($arr);
// Array ( [0] => John [1] => Tom [2] => Tim )

// One-liner with array_splice (better for numeric)
$arr = ['John', 'Jacob', 'Tom', 'Tim'];
array_splice($arr, 1, 1); // Removes AND re-indexes
print_r($arr);

विधि 5: Reference द्वारा Remove (Loop में)

<?php
$arr = ['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4];

// Foreach by reference - modify original
foreach ($arr as $key => &$value) {
    if ($key === 'b' || $key === 'd') {
        unset($arr[$key]); // Safe: modifying array being iterated by reference
    }
}
unset($value); // Break reference

print_r($arr); // [a => 1, c => 3]

Comparison Table

सावधानियां

• Foreach by value पर unset न करें - undefined behavior
• Reference loop के बाद unset($value) करें
• Associative arrays के लिए re-index न करें जब तक जरूरी न हो
• Null check: unset($arr[$key] ?? null) safe है