The implode() function in PHP is used to join elements of an array into a single string. You can specify a glue (a string used to join the elements).

Syntax

implode(string $separator, array $array): string

Note: $separator is optional in some PHP versions; however, it’s recommended to always provide it for clarity.

✅ Basic Example

$fruits = ['apple', 'banana', 'mango'];
$result = implode(", ", $fruits);
echo $result;  // Output: apple, banana, mango

✅ Using Different Separator

$numbers = [1, 2, 3, 4, 5];
echo implode(" - ", $numbers);  // Output: 1 - 2 - 3 - 4 - 5

✅ Without Separator (Empty String)

$letters = ['H', 'E', 'L', 'L', 'O'];
echo implode("", $letters);  // Output: HELLO

✅ Using Implode with Associative Array

$data = ['name' => 'John', 'age' => 30];
echo implode(", ", $data);  // Output: John, 30

It ignores the keys and just joins the values.

✅ Alternative Syntax (PHP < 7.4)

$colors = ['red', 'green', 'blue'];
echo implode($colors); // Output: redgreenblue (if separator not passed)

Older versions allowed implode(array $array, string $separator), but the separator-first version is preferred.

💡 Use Case Example: Converting array for SQL IN clause

$ids = [101, 102, 103];
$sql = "SELECT * FROM users WHERE id IN (" . implode(", ", $ids) . ")";
echo $sql;
// Output: SELECT * FROM users WHERE id IN (101, 102, 103)