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. View all references 

$content = apply_filters( 'the_content', $content );

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Used By

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

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

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

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

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

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

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

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: 2You 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;
}
  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 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 .' =&gt; '. $value .'';
            }
        }
    }

    return $content . $custom_fields;
}
add_filter( 'the_content', 'wpdocs_display_all_custom_fields' );
  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 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' );
?>
  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 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;
}
  9. Skip to note 9 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 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.

  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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