php - what is the difference between printing from a class or returning the output and printing from a function -

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i've created class takes output frpm mysql query , formats , returns it.

here's class:

<?php  class sql_output_two_rows extends sql {      function __construct($sql) {         $this->sql = $sql;         $this->output = "";         parent::__construct($this->sql);         $this->output .=  "<table class='tablenarrow bordered'>\n";         $this->output .= "<tr>\n";         ($f = 0; $f < $this->num_fields; $f++) {             if($f%($this->num_fields/2) == 0){                 $this->output .=  "<tr>\n";             }             if($f>0 && $f%($this->num_fields/2) != (($this->num_fields/2) - 1) || $f == ($this->num_fields - 1)){                 $this->output .= "<th style='border-radius:0px;'>".$this->field_name[$f]."</th>\n";             }else{                 $this->output .= "<th>".$this->field_name[$f]."</th>\n";             }             if($f%($this->num_fields/2) == (($this->num_fields/2) - 1) ){                 $this->output .=  "</tr>\n";             }         }         $this->output .="</tr>\n";         ($r = 0; $r < $this->num_rows; $r++) {             ($f = 0; $f < $this->num_fields; $f++) {                 if($f%($this->num_fields/2) == 0){                     $this->output .=  "<tr style='background:#dbe1ef;'>\n";                 }                 $this->output .= "<td>\n";                 if($this->row_array[$r][$f] == ""){                     $this->row_array[$r][$f]="&nbsp;";                 }                 $this->output .= $this->row_array[$r][$f];                 $this->output .= "</td>\n";                 if($f%($this->num_fields/2) == (($this->num_fields/2) - 1) ){                     $this->output .=  "</tr>\n";                 }             }             $this->output .=  "<tr>\n";             $this->output .= "<td colspan = '".($this->num_fields/2)."'>\n";             $this->output .= "<hr>\n";             $this->output .= "</td>\n";             $this->output .=  "</tr>\n";         }         $this->output .= "</table>\n";         // print $this->output;         return($this->output);     } } ?>

notice last 2 lines of class.

i've commented out line prints output. if uncomment line, call class thus:

new sql_output_two_rows("select * accounts limit 10");

it prints out fine.

however, if leave is, , call thus:

$output = new sql_output_two_rows("select * cameron.accounts limit 10");  print $output . "\n";

then following error:

object of class sql_output_two_rows not converted string

to overcome this, have add functionality class:

 public function __tostring(){      return $this->output;  }

my question this: happening make 1 work - ie when print class - , other not - ie when return output.

i hope i'm clear enough.

instead of printing $output should print $output->output more semantic way write be:

$sqloutput = new sql_output_two_rows("select * accounts limit 10"); print $sqlouput->output;

the reason works because, written, $output contains reference object sql-ouput_two_rows has attribute of $output. in php access object attributes -> arrow. ie: $output->output


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