PHP execution shortcode for WordPress Usage: [php]<?php echo 'Hello World!'; ?>[/php]

gistfile1.php

add_shortcode(
  'php',
	function( $atts, $content = null ){
		// un-texturize $content
		$char_codes   = array( '‘', '’', '“', '”', '′', '″' );
		$replacements = array( "'", "'", '"', '"', "'", '"' );
		$content = str_replace( $char_codes, $replacements, $content );

		// decode html-entities
		$content = html_entity_decode( $content );

		// remove whitespaces at start & end
		$content = trim( $content );

		// remove open tag if present
		if ( true == ( '<?php' == substr( $content, 0, 5 ) ) )
			$content = str_replace( '<?php', '', $content );

		ob_start();
		eval ($content);
		return ob_get_clean();
	}
);