View file vendor/laravel/framework/src/Illuminate/Database/Grammar.php

<?php

namespace Illuminate\Database;

use Illuminate\Database\Query\Expression;
use Illuminate\Support\Traits\Macroable;

abstract class Grammar
{
    use Macroable;

    /**
     * The grammar table prefix.
     *
     * @var string
     */
    protected $tablePrefix = '';

    /**
     * Wrap an array of values.
     *
     * @param  array  $values
     * @return array
     */
    public function wrapArray(array $values)
    {
        return array_map([$this, 'wrap'], $values);
    }

    /**
     * Wrap a table in keyword identifiers.
     *
     * @param  \Illuminate\Database\Query\Expression|string  $table
     * @return string
     */
    public function wrapTable($table)
    {
        if (! $this->isExpression($table)) {
            return $this->wrap($this->tablePrefix.$table, true);
        }

        return $this->getValue($table);
    }

    /**
     * Wrap a value in keyword identifiers.
     *
     * @param  \Illuminate\Database\Query\Expression|string  $value
     * @param  bool  $prefixAlias
     * @return string
     */
    public function wrap($value, $prefixAlias = false)
    {
        if ($this->isExpression($value)) {
            return $this->getValue($value);
        }

        // If the value being wrapped has a column alias we will need to separate out
        // the pieces so we can wrap each of the segments of the expression on its
        // own, and then join these both back together using the "as" connector.
        if (stripos($value, ' as ') !== false) {
            return $this->wrapAliasedValue($value, $prefixAlias);
        }

        return $this->wrapSegments(explode('.', $value));
    }

    /**
     * Wrap a value that has an alias.
     *
     * @param  string  $value
     * @param  bool  $prefixAlias
     * @return string
     */
    protected function wrapAliasedValue($value, $prefixAlias = false)
    {
        $segments = preg_split('/\s+as\s+/i', $value);

        // If we are wrapping a table we need to prefix the alias with the table prefix
        // as well in order to generate proper syntax. If this is a column of course
        // no prefix is necessary. The condition will be true when from wrapTable.
        if ($prefixAlias) {
            $segments[1] = $this->tablePrefix.$segments[1];
        }

        return $this->wrap($segments[0]).' as '.$this->wrapValue($segments[1]);
    }

    /**
     * Wrap the given value segments.
     *
     * @param  array  $segments
     * @return string
     */
    protected function wrapSegments($segments)
    {
        return collect($segments)->map(function ($segment, $key) use ($segments) {
            return $key == 0 && count($segments) > 1
                            ? $this->wrapTable($segment)
                            : $this->wrapValue($segment);
        })->implode('.');
    }

    /**
     * Wrap a single string in keyword identifiers.
     *
     * @param  string  $value
     * @return string
     */
    protected function wrapValue($value)
    {
        if ($value !== '*') {
            return '"'.str_replace('"', '""', $value).'"';
        }

        return $value;
    }

    /**
     * Convert an array of column names into a delimited string.
     *
     * @param  array  $columns
     * @return string
     */
    public function columnize(array $columns)
    {
        return implode(', ', array_map([$this, 'wrap'], $columns));
    }

    /**
     * Create query parameter place-holders for an array.
     *
     * @param  array  $values
     * @return string
     */
    public function parameterize(array $values)
    {
        return implode(', ', array_map([$this, 'parameter'], $values));
    }

    /**
     * Get the appropriate query parameter place-holder for a value.
     *
     * @param  mixed  $value
     * @return string
     */
    public function parameter($value)
    {
        return $this->isExpression($value) ? $this->getValue($value) : '?';
    }

    /**
     * Quote the given string literal.
     *
     * @param  string|array  $value
     * @return string
     */
    public function quoteString($value)
    {
        if (is_array($value)) {
            return implode(', ', array_map([$this, __FUNCTION__], $value));
        }

        return "'$value'";
    }

    /**
     * Determine if the given value is a raw expression.
     *
     * @param  mixed  $value
     * @return bool
     */
    public function isExpression($value)
    {
        return $value instanceof Expression;
    }

    /**
     * Get the value of a raw expression.
     *
     * @param  \Illuminate\Database\Query\Expression  $expression
     * @return string
     */
    public function getValue($expression)
    {
        return $expression->getValue();
    }

    /**
     * Get the format for database stored dates.
     *
     * @return string
     */
    public function getDateFormat()
    {
        return 'Y-m-d H:i:s';
    }

    /**
     * Get the grammar's table prefix.
     *
     * @return string
     */
    public function getTablePrefix()
    {
        return $this->tablePrefix;
    }

    /**
     * Set the grammar's table prefix.
     *
     * @param  string  $prefix
     * @return $this
     */
    public function setTablePrefix($prefix)
    {
        $this->tablePrefix = $prefix;

        return $this;
    }
}