The SplHeap::key() function is an inbuilt function in PHP which is used to get the current node index.
Generally, the Heap Data Structure are of two types:
- Max-Heap: In a Max-Heap the key present at the root node must be greatest among the keys present at all of its children. The same property must be recursively true for all sub-trees in that Binary Tree.
- Min-Heap: In a Min-Heap the key present at the root node must be minimum among the keys present at all of its children. The same property must be recursively true for all sub-trees in that Binary Tree.
Syntax:
mixed SplHeap::key()
Parameters: This function does not accept any parameter.
Return Value: This function returns the key of current node.
Below programs illustrate the SplHeap::key() function in PHP:
Example 1:
PHP
<?php   // Create a new empty Mix Heap $heap = new SplMinHeap();   $heap->insert('System'); $heap->insert('GFG'); $heap->insert('ALGO'); $heap->insert('C'); $heap->insert('Geeks'); $heap->insert('neveropen');   // Loop to display the current element of heap for ($heap->top(); $heap->valid(); $heap->next()) {     echo "Key => " . $heap->key()         . ", Value => " . $heap->current() . "\n"; }   ?> |
Output:
Key => 5, Value => ALGO Key => 4, Value => C Key => 3, Value => GFG Key => 2, Value => Geeks Key => 1, Value => neveropen Key => 0, Value => System
Example 2:
PHP
<?php   // Create a new empty Max Heap $heap = new SplMaxHeap();   $heap->insert('System'); $heap->insert('GFG'); $heap->insert('ALGO'); $heap->insert('C'); $heap->insert('Geeks'); $heap->insert('neveropen');   // Loop to display the current element // of heap with key for ($heap->top(); $heap->valid(); $heap->next()) {     echo "Key => " . $heap->key()         . ", Value => " . $heap->current() . "\n"; }   ?> |
Output:
Key => 5, Value => System Key => 4, Value => neveropen Key => 3, Value => Geeks Key => 2, Value => GFG Key => 1, Value => C Key => 0, Value => ALGO
