Recovery of certain values in an PHP array

[windows_user]

I have a table containing several groups of numbers such
3 4 5 6 7 8 9 15 16 17 18 19 20 52 53 54 55 56 57 58

I get the first and last element of each group of numbers in a new table. In my example, I therefore in my new table 3 9 15 20 52 58

That is what I wrote but it does not work.

$tab1 = array (); 
  $i = 1; 
  $j = 0; 
  $debut1 = current ($tab); // first element of my first table 
  $val = $debut1; 
  $val2 = $val + $i; 
  foreach ($tab as $value) 
  { 
  $val2 = $val + $i; 
  $val3 = next ($ tab); 
  if ($val3 = $val2) 
  { 
  $i++; 
  $tab1 [ $j ] = $val; 
  } 
  else 
  { 
  $j++; 
  $tab1 [ $j ] =prev ( $tab ); 
  $val = current ($tab); 
  }
  } 

[kelfro]

These numbers come from where? you need to do this for what? I ask this because there are several ways to do so I prefer to ask more details to make it match what you need

[fellah]

I have a table containing several groups of numbers such
3 4 5 6 7 8 9 15 16 17 18 19 20 52 53 54 55 56 57 58

How groups are defined and identified?

[opaper]

Just try this. I suppose it should definitely work.

$tab = array (); 
  $tab [0] ='3 4 5 6 7 8 9 '; 
  $tab [1] ='15 16 17 18 19 20 '; 
  $tab [2] ='52 53 54 55 56 57 58 '; 

  for ($i = 0; $i <count ($tab); $i++) 
  { 
          $vals = array (); 
          $vals = explode ( "", $tab [$i]); 
          $val1 = $vals [0]; 
          $val2 = $vals [count ($vals) - 1]; 

          // Val1 and val2 contain here the first and last value 
  }