PHP 5 Constants. Constants are like variables except that once they are defined they cannot be changed or undefined. PHP Constants. A constant is an identifier (name) for a simple value. The value cannot be changed during the script. A valid constant name starts with a letter or underscore (no $ sign before the constant name). Note: Unlike variables, constants are automatically global across the entire script. Create a PHP Constant.
Pressure sores that do not heal may also cause sinus tracts to form. Sinus tracts are passages that connect the infected area of the skin surface or the sore to other structures, such as those deep in the body. For example, a sinus tract from a pressure sore near the pelvis can connect to the bowel.
Things that cause pressure sores include: 1  Pressure on the skin and tissues. 2  This is the most common cause. 3  Sliding down in a bed or chair, which can cause the skin to fold over itself (shear force). Pressure on the skin and tissues. 2  This is the most common cause. 3  Sliding down in a bed or chair, which can cause the skin to fold over itself (shear force). 4  Being pulled across bed sheets or other surfaces, which can cause friction burns. 5  Excess moisture, such as from sweat, urine, or feces.