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Allow to use associative arrays beside indexed arrays in wp_mail $headers #9971

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Allow to use associative arrays beside indexed arrays in wp_mail $headers #9971

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9c84dc6
Add Tests
SirLouen Aug 7, 2025
657f092
Add First Code Version, needs more work
SirLouen Aug 7, 2025
1b29a91
Associative Array Case
SirLouen Sep 20, 2025
811ff70
Little fix
SirLouen Sep 20, 2025
2c982bb
Merging Conditional
SirLouen Sep 20, 2025
a08a6ce
Autocomplete mistake
SirLouen Sep 20, 2025
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14 changes: 11 additions & 3 deletions src/wp-includes/formatting.php
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Original file line number Diff line number Diff line change
Expand Up @@ -6171,13 +6171,21 @@ function wp_staticize_emoji_for_email( $mail ) {
}
}

foreach ( $headers as $header ) {
if ( ! str_contains( $header, ':' ) ) {
foreach ( $headers as $key => $header ) {
if ( is_string( $header ) &&
strpos( $header, ':' ) === false &&
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@westonruter westonruter Oct 13, 2025

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Why switch to strpos() from str_contains()?

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@SirLouen SirLouen Oct 13, 2025

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Having this option, why using a PHP 8.0 function?

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@peterwilsoncc peterwilsoncc Oct 13, 2025

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WordPress includes a polyfill for str_contains()

wordpress-develop/src/wp-includes/compat.php

Lines 402 to 422 in 6b006e9

if ( ! function_exists( 'str_contains' ) ) {
/**
* Polyfill for `str_contains()` function added in PHP 8.0.
*
* Performs a case-sensitive check indicating if needle is
* contained in haystack.
*
* @since 5.9.0
*
* @param string $haystack The string to search in.
* @param string $needle The substring to search for in the `$haystack`.
* @return bool True if `$needle` is in `$haystack`, otherwise false.
*/
function str_contains( $haystack, $needle ) {
if ( '' === $needle ) {
return true;
}
return false !== strpos( $haystack, $needle );
}
}

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@SirLouen SirLouen Oct 13, 2025 •
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Yep, I knew that it used a polyfill that triggers that exact function. This is why it makes no sense to me to use str_contains in this context.

Also, now I remember that the original patch using strpos was made like one decade ago, and I felt that most of the logic was very appropriate, so I preferred to preserve it.

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@peterwilsoncc peterwilsoncc Oct 13, 2025

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Yep, I knew that it used a polyfill that triggers that exact function. This is why it makes no sense to me to use str_contains in this context.

Why are you reluctant to use it?

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@SirLouen SirLouen Oct 13, 2025

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Yep, I knew that it used a polyfill that triggers that exact function. This is why it makes no sense to me to use str_contains in this context.

Why are you reluctant to use it?

Not reluctant. Simply in the original logic in pluggable.php, it was using strpos, so I respected, and wanted to match both scenarios. Since its basically identical, I don't really care one or another.

is_numeric( $key )
) {
continue;
}

// Explode them out.
list( $name, $content ) = explode( ':', trim( $header ), 2 );
list( $name, $content ) = ( is_numeric( $key ) ) ? explode( ':', trim( $header ), 2 ) : array( $key, $header );

// Skip because Content-Type must be an string.
if ( ! is_string( $name ) || ! is_string( $content ) ) {
Comment on lines +6185 to +6186
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@westonruter westonruter Oct 13, 2025

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What if someone $content here is array( 'text/html' )?

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@SirLouen SirLouen Oct 13, 2025

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Can you show me an example of how you can make this array possible?

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@westonruter westonruter Oct 14, 2025

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Per the Trac ticket description: https://core.trac.wordpress.org/ticket/30128

$headers = [
	'From' => 'Me Myself <me@example.net>',
	'Cc'   => [
		'John Q Codex <jqc@wordpress.org>',
		'iluvwp@wordpress.org',
	],
];

What if someone provided:

$headers = [
	'Content-Type' => [
		'text/html',
	],
	'Cc'   => [
		'John Q Codex <jqc@wordpress.org>',
		'iluvwp@wordpress.org',
	],
];

Where arrays are used for every value for consistency.

Relatedly, there's some interesting behaviors when you try to send multiple Content-Type headers, as I found recently: #8412 (comment)

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@SirLouen SirLouen Oct 15, 2025

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True, I did not consider adding this to the mix, but technically it is plausible.

I will give this a second thought.

continue;
}

// Cleanup crew.
$name = trim( $name );
Expand Down
47 changes: 37 additions & 10 deletions src/wp-includes/pluggable.php
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Original file line number Diff line number Diff line change
Expand Up @@ -306,16 +306,20 @@ function wp_mail( $to, $subject, $message, $headers = '', $attachments = array()
// If it's actually got contents.
if ( ! empty( $tempheaders ) ) {
// Iterate through the raw headers.
foreach ( (array) $tempheaders as $header ) {
if ( ! str_contains( $header, ':' ) ) {
foreach ( (array) $tempheaders as $key => $header ) {
if ( is_array( $header ) ) {
$header = implode( ',', $header );
} elseif ( strpos( $header, ':' ) === false ) {
if ( false !== stripos( $header, 'boundary=' ) ) {
$parts = preg_split( '/boundary=/i', trim( $header ) );
$boundary = trim( str_replace( array( "'", '"' ), '', $parts[1] ) );
}
continue;
if ( is_numeric( $key ) ) {
continue;
}
}
// Explode them out.
list( $name, $content ) = explode( ':', trim( $header ), 2 );
list( $name, $content ) = ( is_numeric( $key ) ) ? explode( ':', trim( $header ), 2 ) : array( $key, $header );

// Cleanup crew.
$name = trim( $name );
Expand Down Expand Up @@ -359,17 +363,34 @@ function wp_mail( $to, $subject, $message, $headers = '', $attachments = array()
}
break;
case 'cc':
$cc = array_merge( (array) $cc, explode( ',', $content ) );
$cc = array_merge(
(array) $cc,
( is_array( $content ) ) ? $content : explode( ',', $content )
);
break;
case 'bcc':
$bcc = array_merge( (array) $bcc, explode( ',', $content ) );
$bcc = array_merge(
(array) $bcc,
( is_array( $content ) ) ? $content : explode( ',', $content )
);
break;
case 'reply-to':
$reply_to = array_merge( (array) $reply_to, explode( ',', $content ) );
$reply_to = array_merge(
(array) $reply_to,
( is_array( $content ) ) ? $content : explode( ',', $content )
);
break;
default:
// Add it to our grand headers array.
$headers[ trim( $name ) ] = trim( $content );
$name = trim( $name );
$content = trim( $content );
if ( isset( $headers[ $name ] ) ) {
if ( ! is_array( $headers[ $name ] ) ) {
$headers[ $name ] = array( $headers[ $name ] );
}
$headers[ $name ][] = $content;
} else {
$headers[ $name ] = $content;
}
break;
}
}
Expand Down Expand Up @@ -532,7 +553,13 @@ function wp_mail( $to, $subject, $message, $headers = '', $attachments = array()
// Only add custom headers not added automatically by PHPMailer.
if ( ! in_array( $name, array( 'MIME-Version', 'X-Mailer' ), true ) ) {
try {
$phpmailer->addCustomHeader( sprintf( '%1$s: %2$s', $name, $content ) );
if ( is_array( $content ) ) {
foreach ( $content as $value ) {
$phpmailer->addCustomHeader( sprintf( '%1$s: %2$s', $name, $value ) );
}
} else {
$phpmailer->addCustomHeader( sprintf( '%1$s: %2$s', $name, $content ) );
}
} catch ( PHPMailer\PHPMailer\Exception $e ) {
continue;
}
Expand Down
83 changes: 83 additions & 0 deletions tests/phpunit/tests/pluggable/wpMail.php
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Expand Up @@ -555,6 +555,89 @@ public function test_wp_mail_resets_properties() {
$this->assertNotSame( 'user1', $phpmailer->AltBody );
}

/**
* Test that multiple headers with the same name are sent correctly.
*
* @ticket 30128
* @ticket 56779
*/
public function test_wp_mail_with_multiple_same_name_headers() {
$to = 'test@example.com';
$subject = 'Testing Multiple Headers';
$message = 'This is a test message.';
$headers = array(
'x-my-things: thing1',
'x-my-things: thing2',
);

wp_mail( $to, $subject, $message, $headers );

$mailer = tests_retrieve_phpmailer_instance();
$sent_header = $mailer->get_sent()->header;

$this->assertStringContainsString( 'x-my-things: thing1', $sent_header, 'The first header was not sent.' );
$this->assertStringContainsString( 'x-my-things: thing2', $sent_header, 'The second header was not sent.' );
}

/**
* Tests that headers are handled correctly in various formats.
*
* @dataProvider data_wp_mail_header_formats
*
* @ticket 30128
*/
public function test_wp_mail_header_formats( $headers, $expected_strings ) {
wp_mail( 'test@example.com', 'Test', 'Message', $headers );

$mailer = tests_retrieve_phpmailer_instance();
$sent_header = $mailer->get_sent()->header;

foreach ( $expected_strings as $expected_string ) {
$this->assertStringContainsString( $expected_string, $sent_header );
}
}

/**
* Data provider for test_wp_mail_header_formats.
*/
public function data_wp_mail_header_formats() {
return array(
'associative array' => array(
'headers' => array(
'From' => 'Me Myself <me@example.org>',
'Cc' => 'Isaaco Harrelson <iharrel@example.org>',
),
'expected_strings' => array(
'From: Me Myself <me@example.org>',
'Cc: Isaaco Harrelson <iharrel@example.org>',
),
),
'indexed array' => array(
'headers' => array(
'From: Me Myself <me@example.org>',
'Cc: Isaaco Harrelson <iharrel@example.org>',
),
'expected_strings' => array(
'From: Me Myself <me@example.org>',
'Cc: Isaaco Harrelson <iharrel@example.org>',
),
),
'associative array with multiple CCs' => array(
'headers' => array(
'From' => 'Me Myself <me@example.org>',
'Cc' => array(
'Isaaco Harrelson <iharrel@example.org>',
'frederick@wordpress.org',
),
),
'expected_strings' => array(
'From: Me Myself <me@example.org>',
'Cc: Isaaco Harrelson <iharrel@example.org>, frederick@wordpress.org',
),
),
);
}

/**
* Tests that wp_mail() can send embedded images.
*
Expand Down
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