apply_filters( 'the_content', string $content )

Filters the post content.

Contents

Parameters

$content

(string) Content of the current post.

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More Information

This filter is used to filter the content of a post after it is retrieved from the database and before it is printed to the screen.

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Usage

When using this filter it’s important to check if you’re filtering the content in the main query with the conditionals is_main_query() and in_the_loop(). The main post query can be thought of as the primary post loop that displays the main content for a post, page or archive. Without these conditionals you could unintentionally be filtering the content for custom loops in sidebars, footers, or elsewhere.

add_filter( 'the_content', 'filter_the_content_in_the_main_loop', 1 );

function filter_the_content_in_the_main_loop( $content ) {

    // Check if we're inside the main loop in a single Post.
    if ( is_singular() && in_the_loop() && is_main_query() ) {
        return $content . esc_html__( 'I’m filtering the content inside the main loop', 'wporg');
    }

    return $content;
}

 

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Source

File: wp-includes/post-template.php

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Used By

Used By
Used By Description
wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php: WP_REST_Revisions_Controller::prepare_item_for_response()

Prepares the revision for the REST response.
wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php: WP_REST_Attachments_Controller::prepare_item_for_response()

Prepares a single attachment output for response.
wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php: WP_REST_Posts_Controller::prepare_item_for_response()

Prepares a single post output for response.
wp-includes/formatting.php: wp_trim_excerpt()

Generates an excerpt from the content, if needed.
wp-includes/feed.php: get_the_content_feed()

Retrieve the post content for feeds.
wp-includes/post-template.php: the_content()

Displays the post content.
wp-includes/comment.php: do_trackbacks()

Performs trackbacks.
Show 2 more used by Hide more used by

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Changelog

Changelog
Version Description
0.71 Introduced.

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User Contributed Notes

  1. Skip to note 1 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 6You must log in to vote on the helpfulness of this note
    Contributed by jonburnaby —

    You can choose whether $content will have Shortcodes processed before or after your the_content function has executed by setting the Priority in add_filter. The default (10) will process Shortcodes after you have returned $content at the end of your Filter function. A large figure, such as 99, will already have processed Shortcodes before your Filter function is passed $content.

  4. Skip to note 4 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 1You must log in to vote on the helpfulness of this note
    Contributed by SeanM88 —

    Consolidate multiple string replacement filters
    String replacements are a common reason for filtering the_content and with PHP7 you can now consolidate multiple callback functions using preg_replace_callback_array(); if it makes sense to.

    Example:

    add_filter( 'the_content', 'multiple_string_replacements');
function multiple_string_replacements ( $content ) {
	if ( is_single() && in_the_loop() && is_main_query() ) {
		return preg_replace_callback_array([
			// 1. Removes WordPress injected <p> tags surrounding images in post content.
			'/<p>\s*(<a .*>)?\s*(<img .* \/>)\s*(<\/a>)?\s*<\/p>/iU' => function ( &$matches ) {
				return $matches[1] . $matches[2] . $matches[3];
			},
			// 2. Adds custom data-attribute to <p> tags providing a paragraph id number.
			'|<p>|' => function ( &$matches ) {
				static $i = 1;
				return sprintf( '<p data-p-id="%d">', $i++ );
			},
		], $content );
	}
	return $content;
}

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  5. Skip to note 5 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 1You must log in to vote on the helpfulness of this note
    Contributed by arena —

    the info at the bottom of the hook is wrong for most of the hooks :

    Used by 7 functions | Uses 0 functions (At least it could be 0 function … ah ah ah !)

    HERE is what i have for WP 5.1 :
    * (7 is right, 0 is wrong)
    * and i am not counting apply_filters_ref_array (happily there is no for “the_content” )

    apply_filter
    the_content comment.php 2656
    the_content feed.php 191
    the_content formatting.php 3692
    the_content post-template.php 247
    the_content class-wp-rest-attachments-controller.php 310
    the_content class-wp-rest-posts-controller.php 1532
    the_content class-wp-rest-revisions-controller.php 545
    add_filter
    the_content blocks.php 269
    the_content blocks.php 296
    the_content class-wp-embed.php 32
    the_content class-wp-embed.php 39
    the_content default-filters.php 142
    the_content default-filters.php 172
    the_content default-filters.php 173
    the_content default-filters.php 174
    the_content default-filters.php 175
    the_content default-filters.php 176
    the_content default-filters.php 177
    the_content default-filters.php 178
    the_content default-filters.php 519

    There should be an indication of the WP version.

    my doc (WP 5.1) is available here (https://blog.mailpress.org/hooks/wordpress-5-1/) !

  6. Skip to note 6 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 0You must log in to vote on the helpfulness of this note
    Contributed by trebitzki —

    The usage example is misleading. Unless you’re not interested in pages, it should be

    if ( ( is_single() || is_page() ) && in_the_loop() && is_main_query() ) {
...
}

    You should also add a sufficiently high priority to the filter to hook on the_content before rendering happens:

    add_filter( 'the_content', 'filter_the_content_in_the_main_loop', -1 );

function filter_the_content_in_the_main_loop( $content ) {
    // Check if we're inside the main loop in a post or page.
    if ( ( is_single() || is_page() ) && in_the_loop() && is_main_query() ) {
        return $content . esc_html__("I'm filtering the content inside the main loop", "my-textdomain");
    }
    return $content;
}

    This should go in functions.php.
    It took me half a day to figure out why my filter was doing nothing.

  7. Skip to note 7 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 0You must log in to vote on the helpfulness of this note
    Contributed by dch2018 —

    This is also a good hook to use if you want to display custom fields from a plugin (including ACF fields).

    The following example is from Jeff Starr’s plugins course.

    // display all custom fields for each post
function wpdocs_display_all_custom_fields( $content ) {
    $custom_fields = 'Custom Fields';
    $all_custom_fields = get_post_custom();

    foreach ( $all_custom_fields as $key => $array ) {
        foreach ( $array as $value ) {
            if ( '_' !== substr( $key, 0, 1 ) ) {
                $custom_fields .= ''. $key .' => '. $value .'';
            }
        }
    }

    return $content . $custom_fields;
}
add_filter( 'the_content', 'wpdocs_display_all_custom_fields' );

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  8. Skip to note 8 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 0You must log in to vote on the helpfulness of this note
    Contributed by Muhammad Ayoub —

    Using the example to add classes to p tag & h2 tag. 

    <?php
function wpdocs_replace_content( $text_content ) {
	if ( is_page() ) {
		$text = array(
			'<p>' => '<p class="text-danger">',
			'<h2>' => '<h2 class="h2">',
		);

		$text_content = str_ireplace( array_keys( $text ), $text, $text_content );
	}

	return $text_content;
}
add_filter( 'the_content', 'wpdocs_replace_content' );
?>

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  9. Skip to note 9 content
    You must log in to vote on the helpfulness of this noteVote results for this note: 0You must log in to vote on the helpfulness of this note
    Contributed by Chigozie Orunta —

    A useful hook to filter out vulgar words from your site and keep things nice and tidy for your site visitors.

    add_filter( 'the_content', 'wpdocs_filter_vulgar_words' );

function wpdocs_filter_vulgar_words( $content ) {
	$vulgar_words = array( $vulgar_word1, $vulgar_word2, $vulgar_word3, $vulgar_word4 );

	foreach ( $vulgar_words as $word ) {
		$hashed_word = substr( $word, 0, 1 ) . str_repeat( '*', strlen( $word ) - 1 );
		$content = str_replace( $word, $hashed_word, $content );
	}

	return $content;
}
  10. Skip to note 10 content
    You must log in to vote on the helpfulness of this noteVote results for this note: -1You must log in to vote on the helpfulness of this note
    Contributed by renanbessa —

    Using the example below verifies that if the ALT attribute of any image inserted in the content is empty, get the file name.

    function wpdocs_replaceALT( $content ) {

	if ( is_single() && in_the_loop() && is_main_query() ) {

		libxml_use_internal_errors( true );

		$post = new DOMDocument();
		$post->loadHTML( $content );

		$images = $post->getElementsByTagName( 'img' );

		foreach ( $images as $image ) {

			if ( empty( $image->getAttribute( 'alt' ) ) ) {

				$src = $image->getAttribute( 'src' );
				$alt = pathinfo( $src, PATHINFO_FILENAME );

				$image->setAttribute( 'alt', $alt );

			}
		}

		$content = $post->saveHTML();

		return $content;
	}
}
add_filter( 'the_content', 'wpdocs_replaceALT' );

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