Is this an example of a fluent interface?

I have a Class that has within it two methods. The first method grabs an ID that's arriving from a form and, via a select statement, retrieves the name of the table that corresponds to that ID.

The next method's job is to retrieve the column names of the table the previous method has ascertained.

It looks like this:

class TableData {

	public $table_name;

	function TableName()
	{
		global $mysqli;

		$sql="select table_name from tools where id='$_POST[table_id]'";
			if(!$query=$mysqli->query($sql))
			{
				$err=$mysqli->errno.': '.$mysqli->error;
				trigger_error($err, E_USER_WARNING);
			}
		$row=$query->fetch_object();
		$the_name=$row->tool_name;
		
		$this->table_name=$the_name;
	}

	function TableInfo()
	{
		global $mysqli;
		
		$sql = "show columns from $table_name";
		$query = $mysqli->query($sql);
		
		if(!$query)
		{
		$error = $mysqli->errno.': '.$mysqli->error;
		trigger_error($error, E_USER_WARNING);
		}
		
		$data_count=mysqli_num_rows($query);
		
		if($data_count==0)
		{
		trigger_error("you don't have any column names", E_USER_WARNING);
		}
		//return $data_count;
		
		while($show_columns=$query->fetch_object())
		{
		$the_columns[]=$show_columns->Field;
		}
		return $the_columns;
	}
}

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I imagine you could retrieve the name of the table and then pass it on as a variable into a subsequent function, but I'm thinking there's a more elegant way to do this. As I was looking for some answers I stumbled upon the term "fluent interface" and I'm not sure if that's what I'm looking for, but there it is.

Can I set in motion a "daisy chain" of methods by instantiating one Class? If so, how. If not, what are my options in terms of sound programming?
brucegustPHP DeveloperAsked:
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käµfm³d 👽Commented:
"Fluent interfaces" usually have, as you referred to them, a daisy chain of methods that read almost like a sentence. The gist of creating such an interface is that each method returns something that the next method expects as input, or an object to act against. Usually this thing is the object itself. So in reality you are always working with the same instance; you're just chaining together instance method calls. Wiki shows a good example of this.

You'll need to be careful in how you design such an interface as you can easily end up putting too much into the class for the sake of fluency, and ultimately end up violation the single responsibility principle.
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brucegustPHP DeveloperAuthor Commented:
Kaufmed - thanks for getting back with me!

I had already seen the example you referenced on the Wiki page. Thing is, I couldn't figure out how to do it in the context of my scenario.

Going back to that for a moment, I was able to get it to work. Here's my Class:

class TableData {

	public $table_name;

	function TableName()
	{
		global $mysqli;

		$sql="select table_name from tools where id='$_POST[table_id]'";
		if(!$query=$mysqli->query($sql))
			{
				$err=$mysqli->errno.': '.$mysqli->error;
				trigger_error($err, E_USER_WARNING);
			}
		$row=$query->fetch_object();
		$the_name=$row->table_name;
		
		return $the_name;
	}

	function TableInfo($table_name)
	{
		global $mysqli;
		
		$sql = "show columns from $table_name";
		echo $sql;
		$query = $mysqli->query($sql);
		
		if(!$query)
		{
		$error = $mysqli->errno.': '.$mysqli->error;
		trigger_error($error, E_USER_WARNING);
		}
		
		$data_count=mysqli_num_rows($query);
		
		if($data_count==0)
		{
		trigger_error("you don't have any column names", E_USER_WARNING);
		}
		//return $data_count;
		
		while($show_columns=$query->fetch_object())
		{
		$the_columns[]=$show_columns->Field;
		}
		return $the_columns;
	}
}

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And then here's what I instantiated things so I could get my needed result:

$table_stuff=new TableData;
$table_handle=$table_stuff->TableName();
$columns = $table_stuff->TableInfo($table_handle);

It works! But if I were looking to something a little more elegant / streamlined and I wanted one call, one Class and one result, how would that look? Can that be done?
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käµfm³d 👽Commented:
I would expect something more along the lines of:

class TableData {
    private $table_name;
    
    function FetchTableName()
    {
        global $mysqli;

        $sql="select table_name from tools where id='$_POST[table_id]'";
        if(!$query=$mysqli->query($sql))
            {
                $err=$mysqli->errno.': '.$mysqli->error;
                trigger_error($err, E_USER_WARNING);
            }
        $row=$query->fetch_object();
        $table_name=$row->table_name;
        
        return $this;
    }
    
    function GetTableData()
    {
        global $mysqli;
        
        $sql = "show columns from $table_name";
        echo $sql;
        $query = $mysqli->query($sql);
        
        if(!$query)
        {
            $error = $mysqli->errno.': '.$mysqli->error;
            trigger_error($error, E_USER_WARNING);
        }
        
        $data_count=mysqli_num_rows($query);
        
        if($data_count==0)
        {
            trigger_error("you don't have any column names", E_USER_WARNING);
        }
        //return $data_count;
        
        while($show_columns=$query->fetch_object())
        {
            $the_columns[]=$show_columns->Field;
        }

        return $the_columns;
    }
}

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And then used as:

$table = new TableData();
$data = $table->FetchTableName()
              ->GetTableData();

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käµfm³d 👽Commented:
Notice that the first call, FetchTableName, returns the object itself, not any data. Only the last call in the chain returns something other than the object itself.
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Ray PaseurCommented:
This appears in the Wikipedia article:
<?php
class Employee
{
    public $name;
    public $surName; 
    public $salary;
 
    public function setName($name)
    {
        $this->name = $name;
 
        return $this;
    }
 
    public function setSurname($surname)
    {
        $this->surName = $surname;
 
        return $this;
    }
 
    public function setSalary($salary)
    {
        $this->salary = $salary;
 
        return $this;
    }
 
    public function __toString()
    {
        $employeeInfo = 'Name: ' . $this->name . PHP_EOL;
        $employeeInfo .= 'Surname: ' . $this->surName . PHP_EOL;
        $employeeInfo .= 'Salary: ' . $this->salary . PHP_EOL;
 
        return $employeeInfo;
    }
}
 
# Create a new instance of the Employee class:
$employee = new Employee();
 
# Employee Tom Smith has a salary of 100:
echo $employee->setName('Tom')
              ->setSurname('Smith')
              ->setSalary('100');
 
# Display:
# Name: Tom
# Surname: Smith
# Salary: 100

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These scripts below do essentially the same thing.  Look at the notation near the end to see the variations on the code.  When in doubt, I always try to choose the code style that is easier to read and modify.  There's something about integrating a setter method into an echo statement that makes me vaguely queasy.

<?php // demo/temp_brucegust.php
error_reporting(E_ALL);

class Employee
{
    public $name;
    public $surName;
    public $salary;

    public function setName($name)
    {
        $this->name = $name;

        return $this;
    }

    public function setSurname($surname)
    {
        $this->surName = $surname;

        return $this;
    }

    public function setSalary($salary)
    {
        $this->salary = $salary;

        return $this;
    }

    public function __toString()
    {
        $employeeInfo = 'Name: ' . $this->name . PHP_EOL;
        $employeeInfo .= 'Surname: ' . $this->surName . PHP_EOL;
        $employeeInfo .= 'Salary: ' . $this->salary . PHP_EOL;

        return $employeeInfo;
    }
}

# Create a new instance of the Employee class:
$employee = new Employee();

# Employee Tom Smith has a salary of 100:
$employee->setName('Tom')->setSurname('Smith')->setSalary('100');
echo $employee;

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<?php // demo/temp_brucegust.php
error_reporting(E_ALL);

class Employee
{
    public $name;
    public $surName;
    public $salary;

    public function setName($name)
    {
        $this->name = $name;

        return $this;
    }

    public function setSurname($surname)
    {
        $this->surName = $surname;

        return $this;
    }

    public function setSalary($salary)
    {
        $this->salary = $salary;

        return $this;
    }

    public function __toString()
    {
        $employeeInfo = 'Name: ' . $this->name . PHP_EOL;
        $employeeInfo .= 'Surname: ' . $this->surName . PHP_EOL;
        $employeeInfo .= 'Salary: ' . $this->salary . PHP_EOL;

        return $employeeInfo;
    }
}

# Create a new instance of the Employee class:
$employee = new Employee();

# Employee Tom Smith has a salary of 100:
$employee->setName('Tom');
$employee->setSurname('Smith');
$employee->setSalary('100');
echo $employee;

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