Question

I am just trying to get my head round str_replace and curly brackets / braces .
With the following line, I know that typing {the_title} will get replaces with the array $some_runtime_generated_title , but what does the first value mean ($str_template) ?.

str_replace( $str_template, '{the_title}', $some_runtime_generated_title );

Say I wanted to do the following……..

$dog='lassy';
{dog}
would output >> lassy

How would I do that in php ?

Answer 1

A simple use case of str_replace for place holder replacement would look like:

$paramNames = array("{name}", "{year}", "{salutation}");
$paramValues = array("Iain Simpson", "2012", "Alloha");
$text = "{salutation}, {name}! Happy {year}!";
str_replace($paramNames, $paramValues, $text);

$paramNames and $paramValues arrays have same number of values.

A more specific purpose function would be:

/* Processes a text template by replacing {param}'s with corresponding values. A variation fo this function could accept a name of a file containing the template text. */
/* Parameters: */
/*   template - a template text */
/*   params   - an assoc array (or map) of template parameter name=>value pairs */
function process_template($template, $params) {
    $result = $template;
    foreach ($params as $name => $value) {
        // echo "Replacing {$name} with '$value'"; // echo can be used for debugging purposes
        $result = str_replace("{$name}", $value, $result);
    }
    return $result;
}

Usage example:

$text = process_template("{salutation}, {name}! Happy {year}!", array(
    "name" => "Iain", "year" => 2012, "salutation" => "Alloha"
));

Here’s an example of an object-oriented approach:

class TextTemplate {
   private static $left = "{";
   private static $right = "}";
   private $template;

   function __construct($template) {
       $this->template = $template;
   }

   public function apply($params) {
       $placeholders = array();
       $values = array();
       foreach($params as $name => $value) {
           array_push($placeholders, self::$left . $name . self::$right);
           array_push($values, $value);
       }
       $result = str_replace($placeholders, $values, $this->template);
       return $result;
   }
}

Usage example:

$template = new TextTemplate("{salutation}, {name}! Happy {year}!");
$text = $template->apply(array("name" => "Iain", "year" => 2012, "salutation" => "Alloha"));