View file vendor/illuminate/view/Compilers/Concerns/CompilesEchos.php

<?php

namespace Illuminate\View\Compilers\Concerns;

trait CompilesEchos
{
    /**
     * Compile Blade echos into valid PHP.
     *
     * @param  string  $value
     * @return string
     */
    protected function compileEchos($value)
    {
        foreach ($this->getEchoMethods() as $method) {
            $value = $this->$method($value);
        }

        return $value;
    }

    /**
     * Get the echo methods in the proper order for compilation.
     *
     * @return array
     */
    protected function getEchoMethods()
    {
        return [
            'compileRawEchos',
            'compileEscapedEchos',
            'compileRegularEchos',
        ];
    }

    /**
     * Compile the "raw" echo statements.
     *
     * @param  string  $value
     * @return string
     */
    protected function compileRawEchos($value)
    {
        $pattern = sprintf('/(@)?%s\s*(.+?)\s*%s(\r?\n)?/s', $this->rawTags[0], $this->rawTags[1]);

        $callback = function ($matches) {
            $whitespace = empty($matches[3]) ? '' : $matches[3].$matches[3];

            return $matches[1] ? substr($matches[0], 1) : "<?php echo {$this->compileEchoDefaults($matches[2])}; ?>{$whitespace}";
        };

        return preg_replace_callback($pattern, $callback, $value);
    }

    /**
     * Compile the "regular" echo statements.
     *
     * @param  string  $value
     * @return string
     */
    protected function compileRegularEchos($value)
    {
        $pattern = sprintf('/(@)?%s\s*(.+?)\s*%s(\r?\n)?/s', $this->contentTags[0], $this->contentTags[1]);

        $callback = function ($matches) {
            $whitespace = empty($matches[3]) ? '' : $matches[3].$matches[3];

            $wrapped = sprintf($this->echoFormat, $this->compileEchoDefaults($matches[2]));

            return $matches[1] ? substr($matches[0], 1) : "<?php echo {$wrapped}; ?>{$whitespace}";
        };

        return preg_replace_callback($pattern, $callback, $value);
    }

    /**
     * Compile the escaped echo statements.
     *
     * @param  string  $value
     * @return string
     */
    protected function compileEscapedEchos($value)
    {
        $pattern = sprintf('/(@)?%s\s*(.+?)\s*%s(\r?\n)?/s', $this->escapedTags[0], $this->escapedTags[1]);

        $callback = function ($matches) {
            $whitespace = empty($matches[3]) ? '' : $matches[3].$matches[3];

            return $matches[1] ? $matches[0] : "<?php echo e({$this->compileEchoDefaults($matches[2])}); ?>{$whitespace}";
        };

        return preg_replace_callback($pattern, $callback, $value);
    }

    /**
     * Compile the default values for the echo statement.
     *
     * @param  string  $value
     * @return string
     */
    public function compileEchoDefaults($value)
    {
        return preg_replace('/^(?=\$)(.+?)(?:\s+or\s+)(.+?)$/si', 'isset($1) ? $1 : $2', $value);
    }
}