Escaping untrusted data in php for my wordPress theme - wordpress

Question

I have got a comment from someone superior to me who wants me to escape some comment in two php snippets which I have posted below. The problem is I don't know how to do that. Can anyone help me by modifying the snippets.
Comment I got:
Comment #1:
Validate and/or sanitize untrusted data before entering into the database. All untrusted data should be escaped before output.
Code Snippet #1:
<?php
if ( get_header_image() && !('blank' == get_header_textcolor()) ) {
echo '<div class="site-branding header-background-image" style="background-image: url(' . get_header_image() . ')">';
} else {
echo '<div class="site-branding">';
}
?>
Code Snippet #2:
<?php
printf(
/* translators: %1$s = text link: sangeet, URL: http://wordpress.org/themes/sangeet/, %2$s = text link: Kiran Kumar Dash, URL: https://twitter.com/TheKiranDash */
__( 'Theme: %1$s by %2$s', 'sangeet' ),
'' . esc_attr( 'sangeet', 'sangeet' ) . '',
'' . esc_attr__( 'Kiran Kumar Dash', 'sangeet' ) . '' );
?>
Comment #2:
esc all get_permalink() in content.php
Code snippet #3
<?php
if ( !is_single() ) {
echo '<div class="index-box">';
if ( has_post_thumbnail()) {
echo '<div class="small-index-thumbnail clear">';
echo '<a href="' . get_permalink() . '" title="' . __('Read ', 'sangeet') . get_the_title() . '" rel="bookmark">';
echo the_post_thumbnail('index-thumb');
echo '</a>';
echo '</div>';
}
}
?>
My approach:
I used esc_url to esc the get_permalink() in the snippet. Shall I use esc_all? Or esc_url is just fine.
<?php
if ( !is_single() ) {
echo '<div class="index-box">';
if ( has_post_thumbnail()) {
echo '<div class="small-index-thumbnail clear">';
echo '<a href="' . esc_url(get_permalink()) . '" title="' . __('Read ', 'sangeet') . get_the_title() . '" rel="bookmark">';
echo the_post_thumbnail('index-thumb');
echo '</a>';
echo '</div>';
}
}
?>

Answer 1

As requested:
PS. I didnt write this, only advanced it.
Usage:
$user = sanctify($_GET['user']);
Function:
function sanctify($data){
// Fix &entity\n;
$data = str_replace(array('&','<','>'), array('&amp;','&lt;','&gt;'), $data);
$data = preg_replace('/(&#*\w+)[\x00-\x20]+;/u', '$1;', $data);
$data = preg_replace('/(&#x*[0-9A-F]+);*/iu', '$1;', $data);
$data = html_entity_decode($data, ENT_COMPAT, 'UTF-8');
// Remove any attribute starting with "on" or xmlns
$data = preg_replace('#(<[^>]+?[\x00-\x20"\'])(?:on|xmlns)[^>]*+>#iu', '$1>', $data);
// Remove javascript: and vbscript: protocols
$data = preg_replace('#([a-z]*)[\x00-\x20]*=[\x00-\x20]*([`\'"]*)[\x00-\x20]*j[\x00-\x20]*a[\x00-\x20]*v[\x00-\x20]*a[\x00-\x20]*s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:#iu', '$1=$2nojavascript...', $data);
$data = preg_replace('#([a-z]*)[\x00-\x20]*=([\'"]*)[\x00-\x20]*v[\x00-\x20]*b[\x00-\x20]*s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:#iu', '$1=$2novbscript...', $data);
$data = preg_replace('#([a-z]*)[\x00-\x20]*=([\'"]*)[\x00-\x20]*-moz-binding[\x00-\x20]*:#u', '$1=$2nomozbinding...', $data);
// Only works in IE: <span style="width: expression(alert('Ping!'));"></span>
$data = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?expression[\x00-\x20]*\([^>]*+>#i', '$1>', $data);
$data = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?behaviour[\x00-\x20]*\([^>]*+>#i', '$1>', $data);
$data = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:*[^>]*+>#iu', '$1>', $data);
// Remove namespaced elements (we do not need them)
$data = preg_replace('#</*\w+:\w[^>]*+>#i', '', $data);
$data = str_replace('"','',str_replace("'","",$data));
do{
// Remove really unwanted tags
$old_data = $data;
$data = preg_replace('#</*(?:applet|b(?:ase|gsound|link)|embed|frame(?:set)?|i(?:frame|layer)|l(?:ayer|ink)|meta|object|s(?:cript|tyle)|title|xml)[^>]*+>#i', '', $data);
}
while ($old_data !== $data);
// we are done...
return $data;
}