The implode() function joins array elements into a single string with a separator (glue) between each value. It is one of the most common ways to turn lists into readable text, CSV-style output, or HTML fragments.
Join with glue.
Comma, space, <br>.
Join vs split.
Same function.
Keys ignored.
Glue first, then array.
In PHP, implode() concatenates all elements of an array in order, inserting a separator string between each pair of values. The result is always a string—even when the input array is empty (you get ""). Non-string values are cast to string automatically (booleans become 1 or empty, numbers become digit strings).
Think of implode() as the opposite of explode() for simple cases: explode(',', 'a,b,c') makes an array; implode(',', ['a','b','c']) makes a,b,c. For SQL IN (...) lists, prefer prepared statements—not raw implode of user input.
In PHP 8+, the separator must come before the array:
string implode(string $separator, array $array)
// Optional: omit separator (defaults to "")
string implode(array $array)$separator — glue placed between elements (e.g. ", ", "\n", ""). Optional when using the one-argument form.$array — list of values to join. Keys are ignored; only values are used.Returns a string containing all array values joined with the separator between them.
implode(", ", $arr)Readable CSV-style
implode($arr)Concatenate values
implode("\n", $lines)Multiline text
explode(",", $str)String → array
Run these examples in PHP 7+. Each demonstrates a common pattern beginners encounter with implode().
Join field names or tags with a comma and space.
The classic use case: turn an array into a human-readable list.
<?php
$fields = ['lastname', 'email', 'phone'];
$result = implode(', ', $fields);
echo "Result: $result\n";
?>PHP inserts ", " between each element. There is no trailing separator after the last item.
Use implode with HTML tags as glue to wrap each item in <li>.
<?php
$items = ['PHP', 'MySQL', 'JavaScript'];
$html = "<ul><li>" . implode("</li><li>", $items) . "</li></ul>";
echo $html . "\n";
?>The glue </li><li> sits between values; you wrap the result with opening and closing list tags. Escape user content with htmlspecialchars() when items are not trusted.
Edge cases, associative arrays, and explode roundtrips.
Know what implode returns for arrays with zero or one item.
<?php
$many = ['a', 'b', 'c'];
$one = ['solo'];
$empty = [];
echo "Many: '" . implode('|', $many) . "'\n";
echo "One: '" . implode('|', $one) . "'\n";
echo "Empty: '" . implode('|', $empty) . "' (length " . strlen(implode('|', $empty)) . ")\n";
?>A single element returns that value alone with no separator. An empty array returns an empty string—not false or null.
Keys are ignored; only values are joined in internal order.
<?php
$indexed = ['one', 'two', 'three'];
$assoc = ['first' => 'four', 'five', 'third' => 'six'];
echo implode(',', $indexed) . "\n";
echo implode(',', $assoc) . "\n";
?>To include keys in the output (e.g. name=Tom), build key-value pairs manually or use http_build_query() for URL-style strings.
Split a string into an array, modify it, then join it back.
<?php
$original = "apple,banana,cherry";
$parts = explode(",", $original);
$parts[] = "date";
$joined = implode(",", $parts);
echo "Original: $original\n";
echo "Updated: $joined\n";
?>explode() breaks the string on commas; after adding an element, implode() rebuilds the list. This pattern is common for editing comma-separated settings or tags.
DIRECTORY_SEPARATOR is clearer for paths).implode() WorksSeparator string (or omit for empty glue) plus an array of values to join.
Each element becomes a string. Keys are skipped; order follows the array’s internal value order.
PHP concatenates value + glue + value + glue … with no glue after the last value.
Ready to echo, store, or pass to another function.
join() is an alias—identical behavior to implode().implode($array, $separator).null and emits a warning (PHP 8+).IN (...) clauses, use prepared statements with bound parameters—not raw implode of user IDs.The implode() function turns arrays into delimited strings efficiently. Master the separator-first syntax, remember that keys are ignored, and pair it with explode() when you need to split and rejoin text.
Use it for lists, logs, and HTML snippets—and reach for join() when that name reads better in your code.
implode($separator, $array) order in PHP 8+explode() + edit + implode() for simple CSV-style datahttp_build_query() for URL query stringsarray_filter() if empty slots matterimplode()Use these points whenever you join arrays into strings in PHP.
Join with glue.
PurposePHP 8 argument order.
SyntaxSplit vs join.
RelatedKeys ignored.
ArraysSame function.
AliasContinue with join(), explode(), and the rest of the string function reference.
6 people found this page helpful