When compiling PHP with LDAP support on Debian-based systems, developers often encounter the frustrating error:

configure: error: Cannot find ldap libraries in /usr/include

This occurs despite having installed the development headers via:

sudo apt-get install libldb-dev

The key misunderstanding lies in the --with-ldap parameter. While it might seem logical to point to header files:

./configure --with-ldap=/usr/include

This actually expects the LDAP library path, not header files. The development packages typically install headers in /usr/include while libraries go to /usr/lib.

# Install both development packages
sudo apt-get install libldap2-dev libsasl2-dev

# Correct configure command
./configure --with-ldap=/usr/lib \
            --with-ldap-sasl=/usr

Before running configure, verify both headers and libraries are present:

# Check headers
ls -la /usr/include/ldap*.h

# Check libraries
ls -la /usr/lib/x86_64-linux-gnu/libldap*

For custom installations or multiple PHP versions:

./configure \
    --with-ldap=shared,/usr \
    --with-ldap-sasl=/usr \
    LDFLAGS="-L/usr/lib/x86_64-linux-gnu" \
    CPPFLAGS="-I/usr/include -I/usr/include/sasl"

• Using 32-bit libraries on 64-bit systems (or vice versa)
• Forgetting SASL dependencies when LDAP authentication is needed
• Specifying incorrect paths in multi-arch systems

To get more detailed error information during configuration:

make clean
./configure --with-ldap=/usr --enable-debug

Check config.log for specific linker errors that might reveal missing dependencies.

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When compiling PHP with LDAP support on Debian-based systems, developers often encounter the frustrating error:

configure: error: Cannot find ldap libraries in /usr/include

This occurs even after installing development headers via:

sudo apt-get install libldb-dev

The problem stems from a disconnect between header files and actual library binaries. While libldb-dev provides necessary headers like:

ldap.h
ldap_features.h
ldap_schema.h

It doesn't automatically solve the library dependency chain. The configure script needs both headers and the shared object libraries.

Here's what actually works for a proper PHP LDAP compilation:

sudo apt-get install libldap2-dev
sudo apt-get install libsasl2-dev
./configure --with-ldap=shared,/usr

Key differences from the original approach:

• libldap2-dev provides both headers and library binaries
• The --with-ldap parameter points to /usr instead of /usr/include
• shared flag enables dynamic linking

After successful compilation, verify LDAP support:

php -i | grep LDAP

Should return:

LDAP Support => enabled

1. 32-bit vs 64-bit mismatch:

# For 64-bit systems needing 32-bit compatibility:
sudo apt-get install libc6-dev-i386

2. Custom OpenLDAP installations:

# When using custom built OpenLDAP
./configure --with-ldap=/usr/local/openldap

3. SASL authentication requirements:

# If needing SASL support
sudo apt-get install libsasl2-modules-gssapi-mit

Check actual library locations:

ldconfig -p | grep libldap

Sample output should show:

libldap-2.4.so.2 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libldap-2.4.so.2